Search

Y-type hexaferrites with non-collinear conical magnetic structures, which induce electric polarization (P), are prospective single-phase multiferroics with broad applications, such as magnetic sensors, energy convertors, and memory devices, among others. Y-type hexaferrites have attracted considerable attention. In this study, we investigated the magnetoelectric properties of Ba0.7Sr1.3CoZnFe11AlO22 single crystals with Y-type hexaferrite structures by replacing half of Zn2+ ions with Co2+ ions. A transition from a screw order to the ferromagnetic is observed at TN2 = 356 K in Ba0.7Sr1.3CoZnFe11AlO22 single crystals. The electric polarization (P) and magnetoelectric coupling coefficient ( α ) reach a maximum of 130 μC/m2 and 16667 ps/m at T = 30 K and E = 880 kV/m, respectively. Most importantly, the in-plane Hab induced P can be fully reversed by applying in-plane Hab and it maintains a non-zero value even when the applied magnetic field is zero. Since the P does not decay and repeats many times under a fluctuating low magnetic field, it is important for potential applications in new types of non-volatile memory devices.

Summary The dynamics of polarization evolution and rotation in 0.68PbMg1/3Nb2/3O3-0.32PbTiO3 relaxor ferroelectric thin films are studied via in operando synchrotron-based X-ray diffraction with AC electric fields. A frequency-limited suppression of polarization rotation was observed above ultrasonic frequencies ( ≳ 20 kHz). The nature of this suppression is informed by scanning transmission electron microscopy in the zero-field state, where a high density of nanoscale, low-angle domain walls was observed. In combination with switching dynamics studies, the results suggest that the suppression of polarization rotation at ultrasonic frequencies is due to the large activation field needed to move the domain walls when the polarization rotates between different monoclinic phases. These results are critical in understanding piezoelectric relaxation phenomena in relaxor ferroelectrics.

Lead-free piezoelectric thin films of composition (1-x)Bi0.5Na0.5TiO3-xBi0.5K0.5TiO3-0.03SrZrO3 (x = 15, 17.5, 20 and 22.5%) have been created using the sol-gel spin coating approach over a Pt/Ti/SiO2/Si substrate. The X-ray diffraction profiles suggest that a remarkable transition from tetragonal to rhombohedral-phase passing by a morphotropic phase boundary (MPB) occurs at x values from 17.5 to 22.5%. Additionally, the surface morphology, piezoelectric response, ferroelectric behavior, and energy storage properties were also investigated. Piezoresponse force microscopy (PFM) depicted a strong piezoelectric and ferroelectric behavior at a very localized size; at x = 17.5%. The piezoelectric behavior was enhanced and reached values of the recoverable energy storage density (Jrec) and the energy storage efficiency (η) of 3.27 J/cm3, and 39.9%, respectively. Such materials are anticipated to play an important role in lead-free devices.

In this study, we investigate the applicability of the Induced Polarization (IP) imaging method to discriminate between biogeochemically active and inactive areas of a landfill. The elevated amount of degradable organic carbon in landfills results in the development of biogeochemical hot-spots associated with high rates of microbial activity and the generation of landfill gas and leachate as metabolic products. Our results demonstrate that the electrical conductivity is mainly sensitive to the increase in the fluid conductivity associated to leachate production and migration. Whereas images of the polarization effect, expressed in terms of the imaginary component (σ″) or the phase of the complex conductivity (ϕ), reveal the potential to characterize variations in the architecture and biogeochemical activity of the landfill. Correspondingly, biogeochemically active zones (leachable TOC contents above 1500 mg/kg dry waste) are related to high polarization values (σ″ 10 mS/m, ϕ 40 mrads), whereas low leachable TOC contents (300 mg/kg dry waste) in the inactive areas are characterized by low polarization values (σ″ 1 mS/m, 10 ϕ 25). Additionally, landfill sections corresponding to construction and demolition waste (CDW), associated to negligible TOC content, exhibit the lowest polarization response (σ″ 0.1 mS/m, ϕ 15). We prove that IP imaging is a well-suited method for landfill investigations that permits an improved characterization of landfill geometry, variation in waste composition, and the discrimination between biogeochemically active and inactive zones.

Microbial induced carbonate precipitation (MICP) is a promising soil stabilization method performed by stimulating soil microbes that are naturally occurring and ubiquitous in soil systems. The precipitated carbonate acts as a cementation agent to bind loose soil at grain to grain contacts. MICP has been extensively tested and proven in laboratory environments, as well as in limited field trials; however, long term field applications still remain challenging, partly due to quality control and monitoring issues. Induced polarization (IP), an established geophysical method in mineral exploration, is a prime candidate for MICP monitoring and characterization. This study presents the geophysical results of a 15-day field-scale MICP project. The MICP treatment involved the injection of molasses (carbon source for microbial proliferation) and urea in a Ca2+ rich aquifer. IP monitoring successfully delineated, spatially and temporally, the propagation of MICP in the treatment area, while common resistivity measurements failed to capture any MICP related changes. Reduced hydraulic conductivity in the treatment area versus untreated area, further supports that MICP has changed the physical properties of the subsurface. Furthermore, conventional geochemical monitoring as well as X-ray diffraction analysis confirmed carbonate precipitation in samples from discrete wells in the treatment area.

In relativistic heavy ion collisions, the chiral magnetic effect, known as the “CME”, has been extensively searched for over a decade in order to gain insights into the chiral symmetry restoration in the Quark-Gluon-Plasma, the possible local strong parity violation, and the extremely strong magnetic field. Based on the magnetic field direction and its correlation with the reaction plane, the CME has been mostly measured via a charge-dependent azimuthal correlator with respect to the second-order event plane, where experimental results are not yet conclusive due to their dominant background contaminations. Recent experimental efforts from STAR, ALICE, and CMS Collaboration will be discussed in this paper. Moreover, the total angular momentum from a noncentral collision can induce many important effects via its coupling to the particles' spin, e.g., Λ polarization, which provides essential information about properties of this strongly-interacting fluid-like medium. Besides the discovery of this exotic phenomenon, recent preliminary results from the STAR and ALICE experiment will be reviewed.

Zones with low resistivity low contrast (LRLC) are usually overlooked due to the absence of high-end well logging techniques in the older oil/gas fields. The Nyalau Formation outcrop (stratigraphically equivalent to offshore cycles I and II) from Sarawak, offers a good opportunity to identify and characterize LRLC zones through integrated approaches. Seven facies of the Nyalau Formation had been identified, which are: 1) low angle cross-bedded sandstone (CBSS), 2) laminated sandstone (LSS), 3) heterolithic sandstone (HSS), 4) bioturbated sandstone (BSS), 5) clay-rich sandstone (CSS), 6) mudstone (MS), as well as 7) trough CBSS (TCBSS). Apparent resistivity was determined for brine (60 kpm) saturated core plugs at a temperature of 75 °F by employing the sample core induced polarization technique. The measurement of resistivity was calibrated based on offshore salinity , as well as surface and subsurface temperature of the Sarawak. The geological and petrophysical characteristics were analyzed through field observations and lab analyses. The findings of the study revealed that the cutoff value of resistivity found at LRLC zones in Nyalau Formation was 12.6 Ω-m. Accordingly; LSS, BSS, and CSS facies appeared to derive from LRLC zones. The main causes that generate such LRLC zones are laminations, thin bedding, bioturbation , and clay minerals. The dominant effect portrayed by mixed layers of illite/smectite and smectite in LRLC zones could be attributed to their high cation exchange capacity (CEC). Two varying resistivity trends were discovered based on the variances detected in clay types for different facies. A negative correlation was found between resistivity and porosity within high resistivity zones, while a positive relationship within the LRLC zones. Disparity in the resistivity-porosity correlation is deduced to be associated with clay mineralogy . This study suggests that LRLC zones are expected to be present in shallow marine clastic reservoirs of offshore cycles (I and II), where the offshore reflects Nyalau Formation.

Wave propagation in granular materials is known to be dispersive. Micromorphic continuum model based upon granular micromechanics (Misra, A. and P. Poorsolhjouy, Continuum Mech. Thermodyn, 2016. 28(1-2): p. 215-234.) has the ability to describe this dispersion behavior. In this paper we show that the dispersive behavior can be modulated by using electric field when the grains have dielectric properties. To this end, we apply the recently enhanced model that incorporates electro-elastic coupling by connecting microstrain to electric dipole and quadrupole densities due to bound charges in dielectric grains (Romeo, M., Mech. Res. Commun., 2018. 91: p. 33-38.). We particularly investigate the effect of induced polarization that arises due to an imposed electric field. Two cases of dielectric one dimensional infinite rods with the same micromorphic properties have been studied, where case 1 and 2 are in null and nonzero external electric fields, respectively. Parametric studies are performed to understand the contribution of the polarizability (dipole effect), intrinsic quadrupole density, and external electric field on the dispersive behavior of granular media. Results predict an acoustic and an optical branch in the dispersive curve. Polarizability and external electric field are mainly affecting small wavenumber behavior of the wave branches, while quadrupole density alters the behavior of the material at large wavenumbers. A possibility of altering the optical branch to an acoustic branch is also observed, for which instability or attenuation occurs depending upon the direction of the imposed electric field with respect to the wave propagation direction. We find that the location and the width of the frequency band gaps can be altered using external electric field. The possibility of creating or removing frequency band gaps is also shown to exist. The extended theory accounting for electro-elasticity can therefore be utilized as a tool to analyze existing granular media, or to design granular metamaterials, as it systematizes the design process and eliminates ad-hoc manners leading to large data libraries.

The hyperpolarization of nuclear spins using parahydrogen is an interesting effect that allows to increase the magnetic resonance signal by several orders of magnitude. Known as ParaHydrogen And Synthesis Allow Dramatically Enhanced Nuclear Alignment (PASADENA) and ParaHydrogen Induced Polarization (PHIP), the method was successfully used for in vitro analysis and in vivo imaging. In this contribution, we investigated four known and four new variants of Only Parahydrogen SpectroscopY (OPSY) sequences (Aguilar et al., 2007) with respect to the selective preparation of hyperpolarized NMR signal and background suppression. Depending on the method chosen, either anti-phase, in-phase or a mixture of both signals are obtained: anti-phase signals are beneficial to identify hyperpolarized signals and the structure or J-coupling constants; in-phase signals are useful for imaging applications or when the lines are broad. This comprehensive overview of sequences new and old facilitates selecting the right sequence for the task at hand.

International audience; Electrical conductivity and polarization properties of 6 samples from Krafla volcano (Iceland) were measured in the frequency range 1 mHz-45 kHz and compared to the data obtained on various basaltic rock samples from Ha-waii. The results indicate that for altered samples, the surface conductivity, normalized chargeability, and quad-rature conductivity of the core samples scales linearly with the cation exchange capacity, taken as a proxy of the alteration facies. The surface conductivity of fresh samples is also controlled by the cation exchange capacity but their normalized chargeability is influenced by the presence of magnetite, especially for unaltered samples. The temperature dependence of quadrature conductivity and normalized chargeability can be modeled with an Ar-rhenius equation with an activation energy of 16-19 kJ mol −1. The experimental results agree with a model in which the polarization of the metallic and non-metallic grains are both considered in a unified framework. These results are used to interpret two 3D induced polarization surveys performed in the South and East parts of Krafla volcano using two 1.3 km-long cables with 32 electrodes each. The electrical conductivity is in the range 0.3 (clay cap) to 5 × 10 −5 S m −1 (unaltered rock) while the normalized chargeability is typically comprised between 10 −2 (clay cap) and 10 −5 S m −1 (unaltered rock). Induced polarization is used to image porosity and the cation exchange capacity. A long 5.6 km electrical conductivity profile was also performed connecting the two 3D sites and crossing a rhyolitic obsidian ridge called Hrafntinnuhryggur. Hrafntinnuhryggur is characterized by very low conductivity values on the order of 10 −4 S m −1. The long conductivity profile shows the position of the inner and outer caldera rims and the feeder dike of Hrafntinnuhryggur. A self-potential survey performed along this long profile shows no shallow active geothermal features in this area, as expected from the low perme-ability of the clay cap.

The Neoproterozoic Santa-Quiteria Magmatic Arc (SQMA) hosts significant IOA occurrences that were recently documented in their geological, petrographic, geochemical, and geochronological aspects. To advance the understanding of the geologic framework and metallogenetic potential beneath the SQMA, we used an integrated geophysical approach. In this context, this study is the first geophysical evaluation of these occurrences and provides valuable insights into the ore mineralization of this under-researched region. Seven profiles (E-W direction) were acquired using magnetic, resistivity, and induced polarization methods. The results allowed us to integrate the geological map information with the geophysical anomalies at the subsurface. According to the resistivity and IP inversions there are resistive and chargeable bodies at depths ranging from the surface to up to 180 m, and it is possible to associate the IP anomalies in shallow depths to deep magnetic 3D anomalies modeled. Most 3D magnetic anomalies are located on or very close to the IOA occurrences identified on the surface. The positive anomalies on the IP-chargeability map are related with the sites of alterations, shears, and contact zones. In addition, based on geological mapping, there is a correlation between high chargeability values and high magnetic values with iron formations (iron ore). In contrast, the correlation between high chargeability and low magnetic values indicates metal sulfides (including copper). The results presented here is a start point to further exploration work for this mineral system and we can suggest the future development of more dense geophysical data to better characterize it. An exploratory drilling holes campaign should be used in a second stage as a basis for the 3D geological model of this area. These two latter approaches will be crucial to plan the development of the region's mineral potential.

There is a growing demand for an efficient noninvasive method for monitoring stabilization sites. Geophysical monitoring method was applied in a pilot site. Electrical resistivity tomography (ERT) and time-domain induced polarization (TDIP) surveys showed that the topsoil and stabilized soil exhibited an electrical resistivity of 335.7 ± 251.8 and 74.8 ± 16.9 O-m, respectively, and a chargeability of 11.7 ± 7.6 and 6.0 ± 2.3 mV/V, respectively. Both methods distinguished the stabilized layer and topsoil, and 3D ERT and TDIP provided additional information related to the long-term stability of the stabilized site. The influence of the electrode type on electrical resistivity and chargeability noise was negligible. As the water content in the soil increased, the electrical resistivity and chargeability decreased in the stabilized soil, while chargeability increased at a water content of 20–30% in the topsoil. This study highlights the potential of geophysical methods for monitoring stabilized sites.

Although commonly triggered by heavy or long-lasting precipitation events, landslides in clay-rich formations are hardly predictable as their triggering mechanisms are still not fully understood. Hence, detailed information about the internal structure of landslides with high spatial resolution is fundamental for an improved understanding of triggering mechanisms and management. In this context, electrical resistivity tomography (ERT) is a well-established method used for the delineation of lithological interfaces in landslides and changes in water content. However, the quantitative interpretation of the ERT images can be challenging, particularly for clay-rich landslides, considering that the electrical signatures are dominated by the variations in the clay fraction rather than saturation. Moreover, large scale investigations also demand the development of faster surveying techniques. Hence, in this study we discuss the combined investigation of a landslide with low induction number electromagnetic (EMI) mapping and induced polarization (IP) imaging. We investigate the application of such methods to assess subsurface variability across different scales: near surface EMI mapping and their correlation with geomorphological data, whereas IP images are used to investigate the extension at depth from the shallow structures. Measurements are performed at a shallow clay-rich landslide in Lower Austria (Austria), characterized by lithological structures of the Flysch and Gresten Klippen Zone, with both formations known to be highly susceptible to landsliding. The interpretation of the imaging results for data collected along 15 profiles is performed using separately acquired hydrogeological and geotechnical data. We observe a relationship between the electrical properties and geotechnical parameters which permits to delineate areas associated to different weathering stages controlling the groundwater flow. Moreover, spectral induced polarization (SIP) data collected along one transect shows sensitivity to changes in textural composition, such as the fraction of clay minerals. The study shows the suitability of an integrated investigation with EMI mapping and IP imaging in combination with extensive geotechnical data for an improved characterization of subsurface variability and thus, understanding of clay-rich landslides.

The Induced Polarization (IP) method is recognized as a valuable geophysical tool for resource exploration and environmental studies. In many of these studies, the Cole-Cole relaxation expression has been used to describe how subsurface resistivity depends on the frequency of the fields. In this study, we estimate the resolution of the Cole-Cole parameters of simple models measured by three geophysical methods. We compare the Spectral IP (SIP), the time-domain or Transient IP (TIP), and the in-loop Transient Electromagnetic (TEM) methods. In the first two, a current is injected directly into the ground (galvanic), while in the last one, the current is created by electromagnetic induction. The sensitivities and parameter uncertainties are estimated with a Singular Value Decomposition of the sensitivity matrix for a series of homogeneous and two-layered models. In general, the SIP method gives the best parameter resolutions, followed by those of the TIP and TEM methods. Of the four Cole-Cole parameters, generally the time constant is the least well resolved. The parameters are better resolved when the time constant is less than 10 s. When the polarizable medium is buried under a non-polarizable layer, the uncertainties of the TEM method show an important increase.

Tissue engineering is evolving towards the production of smart platforms exhibiting stimulatory cues to guide tissue regeneration. This work explores the benefits of electrical polarization to produce more efficient neural tissue engineering platforms. Poly ( l -lactic) acid (PLLA)-based scaffolds were prepared as solvent cast films and electrospun aligned nanofibers, and electrically polarized by an in-lab built corona poling device. The characterization of the platforms by thermally stimulated depolarization currents reveals a polarization of 60 × 10−10C cm−2 that is stable on poled electrospun nanofibers for up to 6 months. Further in vitro studies using neuroblastoma cells reveals that platforms’ polarization potentiates Retinoic Acid-induced neuronal differentiation. Additionally, in differentiating embryonic cortical neurons, poled aligned nanofibers further increased neurite outgrowth by 30% (+70 μm) over non-poled aligned nanofibers, and by 50% (+100 μm) over control conditions. Therefore, the synergy of topographical cues and electrical polarization of poled aligned nanofibers places them as promising biocompatible and bioactive platforms for neural tissue regeneration. Given their long lasting induced polarization, these PLLA poled nanofibrous scaffolds can be envisaged as therapeutic devices of long shelf life for neural repair applications.

In this paper, we compared Time Domain Induced Polarization (IP) data obtained from a collection of natural samples that contained pyrite with X-ray micro-Computed Tomography (CT) data. Induced polarization allowed us to obtain the relaxation time distribution and the total chargeability. Computed Tomography enabled us to assess the volumetric content of pyrite and the distribution of the pyrite grains. Comparison of the total chargeability and the volumetric pyrite content revealed a non-linear relationship between these parameters, which we initially attributed to the chargeability of the rock matrix and to anisotropy of some of the samples. Further data analysis, based on a comparison of the Relaxation Time Distributions (RTD) obtained from IP data with those computed based on CT data, revealed the following: (a) for the samples containing pyrite veinlets, the characteristic particle size that allowed the best agreement between the IP-based and synthetic RTDs was 1/2 of the veinlet length; (b) for the samples containing rounded pyrite particles, characteristic size was the Sauter radius. In some of the samples, the CT data show larger pyrite content compared to the IP-derived data. We believe that part of pyrite particles enclosed in carbonate or quartz shells were fully or partially isolated from the pore water , which precluded charge transfer between the pore water and the pyrite particles, thus reducing the overall polarization effect.

The paper presents the data from the surface and subsurface mapping of this area for the purpose of siting industrial city in the area. The field data collected combine with the borehole data was to successfully apply these to solving geological, environmental and engineering complications posed by the complexity of the subsurface geological structures underlain this area. The Electrical Resistivity, (ER) and Induced Polarization, (IP) data were initially processed using RES2DINV software model to generate the depth to the lithological units together with topographic correction. The 2-D ER and IP data were collected from 23rd April 2017 up until 7th May 2017 covering a total of about 17.6 km along 44 survey lines using ABEM Terrameter SAS4000 for the field measurement. A total of 20 Borehole logs data were recorded to better characterized in-situ, the subsurface geological formations emplaced in the study area. The study area is located at Bagan Datuk, Perak Darul Ridzuan situated on Latitude 2° 44.653'N and Longitudes 104° 28.79' E along the west coast Peninsula Malaysia. The topography of the area is generally flat low–laying and elevation range from about 0 m to 32 m above mean sea level (MSL).

The macroscopic response of 0.83PbMg 1/3 Nb 2/3 O 3 -0.17PbTiO 3 (PMN-17PT) single crystals has been investigated in order to resolve existing controversy about the structural phase transition in the rhombohedral side of (1-x)PbMg 1/3 Nb 2/3 O 3 -xPbTiO 3 phase diagram. The combination of nonlinear dielectric spectroscopy, temperature dependant polarization and strain hysteresis loop measurements and ultrasonic spectroscopy revealed that ferroelectric phase occurs spontaneously in PMN-17PT single crystals. The experimental techniques applied in this work probe the bulk of the sample and can unambigously determine the existence of a spontaneous ferroelectric phase. The experiments showed that zero-field cooled sample has a normal ferroelectric hysteresis loop at room temperature. The electric-field dependence of induced polarization revealed that at a certain electric field the sample undergoes transformation from polydomain to monodomain-like states. The 1 s t order phase transition at 330 K was evidenced by the third order nonlinear dielectric susceptibility for monodomain sample. The nonlinear dielectric response of an unpoled sample does not show such abrupt jump and is more similar to the response of canonical relaxor PbMg 1/3 Nb 2/3 O 3 . Zero-field heating and zero-field cooling experiments also revealed very slow domain formation processes appearing at 300–320 K temperature. They are affected by the experimental conditions. There are evidences that on cooling the domains tend to grow in the sample.

At the Negratin Dam (southern Spain) two main springs derived from the water reservoir were detected on the west side of the mountain ridge, matching the location of the left abutment of the dam. The seepages appear when the level of the stored water exceeds 622 m above sea level (m a.s.l.), where some paleochannels are embedded in the silts. The water level was at 631 m a.s.l. on the day of the measurements (13/12/23), close to the historical maximum (633.78 m a.s.l.). Although the water crossing the leaks does not drag particles nowadays, this sector may potentially cause internal erosion or piping phenomena implying a loss of water resources and slope instability problems. The infiltration areas were evaluated by electrical resistivity and induced polarization methods, measured along one profile on the mountain ridge between the water reservoir and the springs. We determine that the infiltrations zones are characterized by low resistivity and high chargeability distributed in small areas. We demonstrate that these methods are a reliable tool to detect and characterize infiltration zones, and they are the first step to planning mitigation actions to avoid the piping phenomena.

Induced polarization (IP) surveys, measuring overvoltage phenomena of the medium, are widely and increasingly performed not only for exploration of mineral resources but also for engineering applications. Among several IP survey methods such as time-domain, frequency-domain and spectral IP surveys, this study introduces a noble inversion method for time-domain IP data to recover the chargeability structure of target medium. The inversion method employs the concept of 4D inversion of time-lapse resistivity data sets, considering the fact that measured voltage in time-domain IP survey is distorted by IP effects to increase from the instantaneous voltage measured at the moment the source current injection starts. Even though the increase is saturated very fast, we can consider the saturated and instantaneous voltages as a time-lapse data set. The 4D inversion method is one of the most powerful method for inverting time-lapse resistivity data sets. Using the developed IP inversion algorithm, we invert not only synthetic but also field IP data to show the effectiveness of the proposed method by comparing the recovered chargeability models with those from linear inversion that was used for the inversion of the field data in a previous study. Numerical results confirm that the proposed inversion method generates reliable chargeability models even though the anomalous bodies have large IP effects.

In this paper, we demonstrate the effect of polarization conversion in a plasmonic metasurface structure, in which each unit cell consists of a metal bar and four metal split-ring resonators (SRRs). Such effect is attributed to the fact that the dark plasmon mode of SRRs (bar), which radiates cross-polarized component, is induced by the bright plasmon mode of bar (SRRs) due to the electromagnetic near-field coupling between bar and SRRs. We find that there are two ways to achieve a large cross-polarized component in our proposed metasurface structure. The first way is realized when the dark plasmon mode of bar (SRRs) is in resonance, while at this time the bright plasmon mode of SRRs (bar) is not at resonant state. The second way is realized when the bright plasmon mode of SRRs (bar) is resonantly excited, while the dark plasmon mode of bar (SRRs) is at nonresonant state. It is also found that the linearly polarized light can be rotated by 56.5 0 after propagation through the metasurface structure. Furthermore, our proposed metasurface structure exhibits an asymmetric transmission for circularly polarized light. Our findings take a further step in developing integrated metasurface-based photonics devices for polarization manipulation and modulation.

Mine waste rock piles (WRPs) can contain sulfidic minerals whose interaction with oxygen and water can generate acid mine drainage (AMD). Thus, WRPs can be a long-term source of environmental pollution. Since the generation of AMD and its release into the environment is dependent on the net volume and bulk composition of waste rock, effective characterization of WRPs is necessary for successful remedial design and monitoring. In this study, a combined DC resistivity and induced polarization (DC-IP) approach was employed to characterize an AMD-generating WRP in the Sydney Coalfield, Nova Scotia, Canada. Two-dimensional (2D) DC-IP imaging with 6 survey lines was performed to capture the full WRP landform. 2D DC results indicated a highly heterogeneous and moderately conductive waste rock underlain by a resistive bedrock containing numerous fractures. 2D IP (chargeability) results identified several highly-chargeable regions within the waste, with normalized chargeability delineating regions specific to waste mineralogy only. Three-dimensional (3D) DC-IP imaging, using 17 parallel lines on the plateau of the pile, was then used to focus on the composition of the waste rock. The full 3D inverted DC-IP distributions were used to identify coincident and continuous zones (isosurfaces) of low resistivity ( 0.4 mS/m) that were inferred as generated AMD (leachate) and stored AMD (sulfides), respectively. Integrated geological, hydrogeological and geochemical data increased confidence in the geoelectrical interpretations. Knowledge on the location of potentially more reactive waste material is extremely valuable for improved long-term AMD monitoring at the WRP. (Less)

The Digha-Shankarur-Tajpur-Mandarmani (DSTM) area in West-Bengal is well known for seawater invasion in shallow aquifers. In the present work, geophysical investigations such as Electrical Resistivity Imaging (ERI) and Induced Polarization (IP) data were used to delineate the possible zones of shallow aquifers contaminated with seawater. Smoothness-constrained least square and unstructured grid-based finite element methods were applied to interpret ERI data. The finite element method based inversion technique adopted in this study is better in terms of the final resolution of interpretation. Furthermore, the resistivity imaging survey showed low resistive zones (0–5 Ωm) in shallow aquifers. Subsequently, the IP data with low chargeability indicates probable zones of seawater invasion. These affected zones are associated mostly with clay and sandy layers up to a depth of 30 m. Moreover, the geophysical data suggests that the seawater invasion zones do not show any linear relationship throughout the area. This is mainly because the anthropogenic activities have overshadow geogenic activities. Hence, human-induced activities should be restricted in the present study area on the landward side to reduce the hazards related to seawater invasion in the groundwater aquifers in the region.

Induced polarization is used to image the feeder dike of a monogenetic dome thanks to the signature of pronounced alteration around these conduits. We performed a 3D tomography of the electrical conductivity and normalized chargeability of the 1630-monogenetic dome located inside the caldera of Furnas, a quiescent stratovolcano in the Eastern side of Sao Miguel Island (Azores volcanic archipelago, Atlantic Ocean). A total of 2634 apparent resistivity and chargeability data were collected and inverted using a classical regularized least-squares inversion (based on a quasi-Gauss-Newton approach). The 3D tomograms display an area of both high electrical conductivity and normalized chargeability. This area corresponds to the altered subvolume associated with the magmatic feeding conduit of the monogenetic dome. The same conduit can be also observed on a 2D magnetotelluric (MT) section, at least for the first 200 m below the ground surface. Assuming that the in-situ pore water conductivity is the same as in Furnas Lake (∼0.016 S m−1, 25 °C), the electrical conductivity and normalized chargeability are combined to obtain tomograms of the water content and cation exchange capacity of the monogenetic dome. The cation exchange capacity provides a proxy to image alteration associated with the formation of clay minerals and zeolites. This study highlights the usefulness of these techniques to image the structure of monogenetic domes.

Direct Current (DC) Resistivity and Induced Polarization (IP) response of six profiles were measured using the Gradient electrode configuration in Adventdalen, Svalbard, to characterise the near-surface stratigraphy of the soil and to account for geotechnical and environmental aspects of global warming in the arctic region. In addition, Wenner array data was collected for the selected profiles to examine its effectiveness as compared to the Gradient array, given the characteristics of the study site. Two commercial inversion software programs, Res2DINV and AarhusINV, were used for the inversion of the DC resistivity and IP data, to compare the software. Physical soil properties, including porosity, water saturation, water salinity, freezing temperature and grain size distribution, previously measured from samples retrieved from wells along the studied profiles, were integrated in this study to investigate the correlation with geoelectrical properties of the sediments inferred from the DC resistivity and IP data. Results from processing of the Wenner array DC resistivity data provided higher resolution as compared to the Gradient array data, especially from deeper parts of the models, due to its higher signal-to-noise ratio. The Wenner array data also indicated better inversion result for the IP data as distinctive anomalies were better indicated in data from Wenner array compared with the Gradient array data. The Wenner array data also provided a realistic trend for the anomalies, thanks to the symmetrical geometry of the electrodes during the survey, although at the cost of time and higher expenses. Inversion results proved that AarhusINV resolved the geometry of the subsurface layers with higher resolution compared with the Res2DINV. However, the two inversion algorithms use slightly different parameters for the processing and for presenting the results, thus only allowing qualitative comparison. Based on the interpretations of the DC resistivity and IP data, four distinctive zones were identified from the surface to the maximum depth of 26 m, consisting of (i) unfrozen active-layer-(silts and sands), with intermediate resistivity values 200–300 Ω·m; (ii) frozen soil with 3–10 m thickness and resistivity values between 2500 and 5000 Ω·m; (iii) unfrozen soil (cryopegs) with high salinity and low resistivity of 40 Ω·m; and finally (iv) clayey-unfrozen soil sediments with low resistivity ranging 10–20 Ω·m, at depths between 13 and 26 m. The IP data allowed for the delineation of a low chargeability zone near the surface and a high chargeability zone at greater depth which denote the active layer, lower parts of unfrozen soil sediments and cryopeg respectively, within the top 10 m of the subsurface. The 3D subsurface model of the study area was created based on interpretations of the DC resistivity and IP data and was constrained by the description of the subsurface stratigraphy from nearby wells, which provided detailed information about the vertical stratigraphy of the study area. In addition, a good correlation was observed between the studied physical properties of the sediments and the DC resistivity data for the intersecting profile SVAER04, as the interface between high and low resistivity data at ca. 10 m depth coincided the sedimentary formation with intermediate-fine grain size, high porosity, high water saturation and high salt content. Our findings show that joint application of the geoelectrical surveys and laboratory analysis of soil samples are an efficient complement to each other. These methods can be used as an alternative to each other to investigate larger areas where achieving high resolution data is not necessary. Our study results underline the importance of choosing the right survey design for collecting the DC resistivity and IP data. Contribution of the IP data in this study mostly concerns the shallow parts of the subsurface due to the low signal-to-noise ratio at greater depths, and frozen ground which limited the ion mobility and hence the IP response. An appropriate inversion program coupled with integration of the physical properties of the sediments, can be successfully applied to characterise the near-surface morphology of the sedimentary formations to address the geotechnical and environmental challenges related to the permafrost in the Arctic.

The induced polarization (IP) method has been widely used in geophysical exploration to identify the chargeable targets such as mineral deposits. The inversion of the IP data requires modeling the IP response of 3D dispersive conductive structures. We have developed an edge-based finite-element time-domain (FETD) modeling method to simulate the electromagnetic (EM) fields in 3D dispersive medium. We solve the vector Helmholtz equation for total electric field using the edge-based finite-element method with an unstructured tetrahedral mesh. We adopt the backward propagation Euler method, which is unconditionally stable, with semi-adaptive time stepping for the time domain discretization. We use the direct solver based on a sparse LU decomposition to solve the system of equations. We consider the Cole-Cole model in order to take into account the frequency-dependent conductivity dispersion. The Cole-Cole conductivity model in frequency domain is expanded using a truncated Pade series with adaptive selection of the center frequency of the series for early and late time. This approach can significantly increase the accuracy of FETD modeling.

The complex conductivity method is frequently used in hydro-/petro-/environmental geophysics, and considered to be a promising tool for characterizing and quantifying the properties of subsurface rocks, sediments and soils. We report a study on the complex conductivity characteristics of porous media containing gas hydrates through numerical modelling. The effects of the hydrate saturation, pore-water salinity and micro-distribution mode were studied, and hydrate-saturation evaluation correlations based on complex conductivity parameters were developed. A pore-scale numerical approach for developing the finite-element based models for hydrate-bearing porous media is proposed and a two-dimensional (2D) model is built to compute the complex conductivity responses of porous media under various conditions. We demonstrate that the simple 2D model can capture the dominant characteristics of the complex conductivity of hydrate-bearing porous media within the frequency range related to the induced polarization. The in-phase conductivity, quadrature conductivity and effective dielectric constant can be correlated with the saturation based on a power law in the log-log space, by which the hydrate-saturation evaluation models can be derived. A constant saturation exponent of the power-law correlation between the hydrate saturation and quadrature conductivity can be obtained when the pore-water conductivity exceeds 1.0 S/m. This is highly desirable in the hydrate-saturation models due to the variations of the pore-water conductivity in the processes of hydrate formation and dissociation. Within the framework of the complex conductivity analysis, the micro-distribution modes of hydrates in porous media can be categorized into two types. These are the fluid-suspending mode and grain-attaching mode. The in-phase conductivity exhibits significant variations under the same saturation and salinity but different micro-distribution modes, which can be attributed to the change in the tortuosity of the electrical conduction paths in the void space of porous media.

Monoclinic distortion stabilized in a compressively strained [111] PbTiO3, for which the polarization vector is confined in a symmetry plane, is investigated using a phenomenological model. Rhombohedral to monoclinic transitions can be induced by stress normal to the film surface when flattening of energy surface reaches a critical barrier level. Two types of monoclinic states close in free energy exhibit opposite direction of induced polarization rotation. The impact of compressive stress on polarization, monoclinic shear strain, and volume change of unit cell is calculated and compared with experimental reports in the literature. Dielectric and piezoelectric anomalies are predicted in the stabilized monoclinic phase.

A study of the orthogonal polarization modes crosstalk changes in the point of different mechanical actions (pressure force) in the polarization-maintaining fiber with straining elliptical cladding is presented. It was found that by increasing of the pressure force the polarization extinction ratio increases nonlinearly. Also revealed the dependence of the extinction coefficient and the angle between vector of the mechanical action and polarization axes of the test fiber, which leads to change the extinction coefficient variable from −57 dB to −25 dB under the pressure force of 0.7 N. Also it was found that the cross angle of the fiber axes doesn’t influence on the extinction ratio value of the mechanical induced polarization crosstalk.

The following work is an attempt to enhance and optimize the potential exploitation of the Hammam Sayala thermal spring (NW Tunisia). This hot spring is located at 10 km of South-western Beja city, with higher temperature values around 42 °C and a low discharge value of about 1 l s −1 . The geological and structural settings of the study area are complex and associated with faults and Triassic intruded salt and evaporate. An integrated geophysical approach using Electrical Resistivity Tomography (ERT), Induced Polarization (IP) and Vertical Electrical Sounding (VES) techniques can provide a high-resolution subsurface image of the principal geothermal plume and associated pathways. These data were used to determine and understand the mechanisms responsible of the rise of hot water flowing out onto the surface. Our results add new information of the hydrothermal system's context in Hammam Sayala area, which can help to create a therapeutic center opening new perspectives in the Beja region and to encourage regional thermal tourism development.

High intensity lasers can induce in solid targets a charge separation resulting in a time-dependent induced polarization. In this work, the characterization of a plastic target subjected to a laser irradiation has been analysed. A focus was particularly devoted to the interaction of the target with the whole grounded chamber, manipulated through the change of the target-holder surface ratio. The targets are thick samples (thickness >1 mm) of polymers arranged in discs according to the metallic holder shape. A possible correlation between the target current and the main features of the produced plasma was analyzed, in order to acquire a deeper knowledge on laser–matter interactions with the laser pulse on the nanosecond scale. Collected signals were analyzed to reconstruct the time evolution of key observables as well as the charge space distribution in the chamber. The experimental setting allowing the target current observation and the measurement procedure is discussed.

Two-dimensional chirality induced polarization conversion and asymmetric transmission have great potential for polarization applications. We propose graphene-based planar chiral metamaterial and its complementary structure with dual functionality of both circular polarization conversion and asymmetric transmission in terahertz (THz) region. The conversion efficiency of chiral structure can reach up to 37.33/λ, which is comparable with three-dimensional chiral structure made of metal due to the unique optoelectronic properties of graphene. The transmission asymmetry of complementary chiral metamaterial originating from the high order plasmonic resonance can be tuned from 0.049% to 3.504% by changing Fermi energy, and the asymmetry can also be enhanced via geometrical optimization. This work raises the prospect of switchable, compact, and on-chip THz polarized devices with graphene materials.

Induced polarization is a geophysical method investigating the ability of rocks to store reversibly electrical charges under a slowly alternating electrical field. The material property of interest is a complex-valued electrical conductivity with an in-phase component associated with conduction and a quadrature component associated with polarization. We investigated the relationship between complex conductivity spectra over the frequency range 1 mHz–45 kHz and the specific surface area (SSA) of 28 volcanic core samples extracted from a wellbore drilled for the Humuʻula Groundwater Research Project in Hawaii. The specific surface area of these samples was determined through the Brunauer, Emmett and Teller (BET) method. Subcritical nitrogen adsorption experiments were conducted using two different instruments and the samples were prepared in both pellets and powder forms. The BET specific surface area is found to be highly correlated to the cation exchange capacity of the core samples measured by the cobalthexamine method. The in-phase conductivity itself can be decomposed as the sum of a bulk contribution associated with conduction in the bulk pore water and a surface conductivity associated with conduction in the electrical double layer coating the grains. The surface conductivity, the quadrature conductivity, and the normalized chargeability (defined as the difference between the in-phase conductivity at high and low frequencies) are observed to be linearly correlated to the specific surface area or the surface per volume ratio of the core samples, which can be considered as proxy of alteration. These trends are consistent with those shown by sedimentary rocks. This new data set demonstrates that the induced polarization method can be potentially used to image alteration in volcanic environments.

Al/CdTe/Pt detectors are very attractive devices for high-resolution X-ray spectroscopy, even though they suffer from polarization phenomena, which cause a progressive time degradation of the spectroscopic performance. In this work we investigated on the time dependence of the electric field of an Al/CdTe/Pt detector under optical perturbation by means of Pockels effect measurements. A tunable laser with wavelengths ranging within 700−1000 nm and a 940 nm light emitting diode (LED) were used. The measurements of both the electric field profile and the total current were used to better understand the effects of the optical perturbation on polarization phenomena. The results point out as the above band-gap light, due to the trapping of photo-generated holes at the anode (the Al/CdTe blocking contact), brings to a reduction of the negative space charge caused by the bias voltage (bias induced polarization) and the LED irradiation (radiation induced polarization). The reduction of the negative space charge ensures a quite stable and uniform electric field distribution, typically termed depolarization. Conversely, optical perturbation with sub-band-gap light enhances the polarization with the formation of two oppositely charged regions within the detector.

Induced polarization shows a significant influence on dielectric permittivity of 0–3 polymer composites containing Si-based semi-conductive fillers. The nature of induced polarization is the increased electric conductivity or decreased band gap in Si-based semi-conductive fillers. In this work, the dependence of induced polarization onto particle size of α-SiC filler together with polarity of polymer matrix and Si-based semi-conductive filler has been elaborately investigated by detecting the permittivity of composites. It was found that increasing the grain size of SiC filler, improving the polarity of polymer matrix and reducing the band-gap of Si-based semi-conductive filler could favor the enhancement of the overall induced polarity in the composites. As a result, the significantly improved dielectric permittivity of composites higher than both of the neat polymer and filler was observed depending on the constituents of the composites. The highest dielectric permittivity of ~215@1 kHz was achieved in poly(vinyl alcohol) based composite filled with 60 vol% of 12 µm SiC particles. The dielectric permittivity of these 0–3 composites could be well tuned in a wide range through altering their constituents. This work might open a facile route to obtain the promising high-performance dielectric composite materials by regulating the degree of induced polarization.

Effects of induced polarization (IP) can have an impact on time-domain electromagnetic measurements (TEM) and may lead to sign reversals in the recorded transients. To study these IP effects on TEM data, a new 1D inversion algorithm was developed for both, the central-loop and the separate-loop TEM configurations using the Cole-Cole relaxation model. 1D forward calculations for a homogeneous half-space were conducted with the aim of analyzing the impacts of the Cole-Cole parameters on TEM transients with respect to possible sign reversals. The forward modelings showed that the variation of different parameters have comparable effects on the TEM transients. This leads to an increasing number of equivalent models as a result of inversion calculations. Subsequently, 1D inversions of synthetic data were performed to study the potentials and limitations of the algorithm regarding the resolution of the Cole-Cole parameters. In order to achieve optimal inversion results, it was essential to error-weight the data points in the direct vicinity of sign reversals. The obtained findings were eventually adopted on the inversion of real field data which contained considerable IP signatures such as sign reversals. One field data set was recorded at the Nakyn kimberlite field in Western Yakutiya, Russia, in the central-loop configuration. Another field data set originates from a waste site in Cologne, Germany, and was measured utilizing the separate-loop configuration.

This study attempted to evaluate the role and effectiveness of induced polarization (IP) along with electrical resistivity to identify soft ground/fractured rock. Theoretical studies as well as laboratory-scale experiments were conducted for this purpose. The theoretical study involved deriving the functional relationship between chargeability and influential variables. This was followed by performing a sensitivity analysis using the derived relationship to reveal that the size of narrow pores (r1) exerted the greatest influence on the chargeability followed by the salinity of the pore water (C0). In the laboratory test, a small-scale fractured rock zone was modeled using sandstone as a parent rock. The chargeability and resistivity were measured by changing the size of the joint aperture filled with tap water and/or sea water, the location of the fractured zone, and the thickness of the soil layer in a soil-rock multi-layered ground. The experimental study modeled the jointed zone between competent sandstone layers and indicated that the chargeability was mostly controlled by the size of the narrow pore (r1) of the surface sandstone and not by the porosity of the jointed zone. Hence, it was concluded that the chargeability did not significantly depend on the fractured characteristics of the jointed rock. It could be difficult to clearly distinguish as to whether the low resistivity value is caused by the sea water intrusion or by the increase in porosity of the fractured ground. However, the IP exploration can be effectively utilized to identify sea water intrusion since the chargeability decreased as the salinity of pore water increased. The experimental study on a soil-rock multi-layered ground indicated that the measured chargeability was controlled by the percentage of current flow that passed through the competent rock as well as by the narrow pore size of the rock itself. In conclusion, the ground condition could be easily identified by measuring the IP in conjunction with the electrical resistivity, and this increased the reliability of identifying the existence of sea water, layered ground, and/or the fractured rock.

Globally, an enormous number of polluted areas are in need of remediation to prevent adverse effects on health and environment. In situ remediation and especially the monitoring thereof needs further development to avoid costly and hazardous shipments associated with excavation. The monitoring of in situ remediation actions needs easier and cheaper nondestructive methods for evaluation and verification of remediation degree and degradation status of the contaminants. We investigate the Direct Current resistivity and time-domain Induced Polarization tomography (DCIP) method and its use within the context of a DNAPL (Dense Non-Aqueous Phase Liquids) contaminated site in Varberg, Sweden, where an in situ remediation pilot test has been performed by stimulated reductive dechlorination by push injection. Our results show that the DCIP technique is an emerging and promising technique for mapping of underground structures and possibly biogeochemical spatial and temporal changes. The methodology could in combination with drilling, sampling and other complementary methods give an almost continuous image of the underground structures and delineation of the pollutant situation. It can be expected to have a future in monitoring approaches measuring time lapse induced polarization (IP), if more research is performed on the parameters and processes affecting the IP-signals verifying the interpretations. The IP technique can possibly be used for verification of the effectiveness of in situ remediation actions, as the current sampling methodology is inadequate.

Room temperature I–V characteristics study, both in presence and absence of magnetic field (1800 Oe), has been performed on NiFe2O4 nanoparticles, having different particle size (Ф~14, 21 and 31 nm). Our experiments on these nanoparticles provide evidences for: (1) electrical irreversibility or hysteretic behaviour; (2) positive magnetoresistance and (3) magnetic field dependent electrical irreversibility or hysteresis in the sample. “Hysteretic” nature of I–V curve reveals the existence of electrical memory effect in the sample. Significantly, such hysteresis has been found to be tuned by magnetic field. In order to explain the observed electrical irreversibility, we have proposed a phenomenological model on the light of induced polarization in the sample. Both the positive magnetoresistance and the observed magnetic field dependence of electrical irreversibility have been explained through magnetostriction phenomenon. Interestingly, such effects are found to get reduced with increasing particle size. For NiFe2O4 nanoparticles having Ф=31 nm, we did not observe any irreversibility effect. This feature has been attributed to the enhanced grain surface effect that in turn gives rise to the residual polarization and hence electrical memory effect in NiFe2O4 nanoparticles, having small nanoscopic particle size.

In order to expand the application of the induced polarization (IP) method as a technique for monitoring metallic mineral dissolution and precipitation mechanisms, we studied the effects of variations in pore water chemistry on the spectral induced polarization (SIP) response of a mixture of silica-sand and pyrite particles in the laboratory. We investigated the dependence of the SIP response on both pore water conductivity and pH for various chemical compositions: redox-passive (P) versus redox-active (A) ions, using CaCl 2 as P-ions, and FeSO4 and FeCl3 as A-ion brines. The effect of pore water chemistry was evaluated by means of a recently proposed volumetric specific capacitance model. The SIP response (IP-effect) was primarily determined by the pore water conductivity and the specific capacitance was only weakly dependent on the chemical composition and pHw. We found that the specific capacitance varies to first order over a limited range and approximates a single value (≈ 302 F m− 3 in average). However, variations in the specific capacitance as a function of active versus inactive ion chemistry might be important to consider when using IP to monitor specific mineral dissolution and precipitation processes.

We performed 2D resistivity and IP measurements over a known olive oil mill waste plume at a site in western Crete, Greece. The objectives of the survey were: (1) to determine whether IP is more diagnostic in delineating the spatial extent of the plume relative to resistivity measurements alone; (2) to evaluate whether the additional information content obtained from IP is worth the effort given longer data acquisition times and higher measurement errors that inevitably characterize field IP data acquisition. Complex conductivity inversion of the field IP dataset revealed that the organic plume is characterized as a region of high electrical conductivity (real part of complex conductivity) consistent with the conceptual model for the electrical structure of a biodegraded LNAPL contaminant plume. The plume is also characterized by a region of high polarizability (imaginary part of complex conductivity) that is more localized to the known plume location (based on conventional monitoring) relative to the high conductivity region in the electrical conductivity image. This observation is attributed to the fact that electrical conductivity is more strongly controlled by hydrogeological and geological characteristics of the site that mask the response from the biodegraded plume. This result encourages the use of field IP to improve the spatial delineation of organic contamination in the subsurface. However, more laborious field procedures are required to acquire reliable field IP data and the inversion of field IP data remains more challenging than resistivity data alone.

The estimation of hydraulic parameters from spectral induced polarization (SIP) measurements is difficult partly because the electrical impedance of sediments depends on several parameters that are not related to the texture. Important parameters that influence the spectral response are fluid salinity and pH. In order to understand the behaviour of SIP spectra from a mechanistic point of view, we carry out simulations with a membrane polarization model. The geometry consists of a sequence of wide and narrow pores with finite radii. The charge distribution at the mineral surface is described by a triple layer model, characterized by the zeta potential and the partition coefficient. We extended an existing model by incorporating known dependencies of the zeta potential and the partition coefficient on fluid salinity and pH. Our simulation results predict a decrease of the maximum phase shift of the complex electrical conductivity with increasing salinity, consistent with experimental observations. For very small pore radii, the phase shift may also show the opposite behaviour and increase with salinity. The imaginary conductivity at 1 Hz increases with increasing salinity, followed by a peak and a decrease at high salinities. The fact that our model predicts a decrease of the imaginary conductivity at high salinities is particularly important, because strong experimental evidence was recently found for such a decrease, which was theoretically unexplained so far. Both the maximum phase shift and the imaginary conductivity at 1 Hz decrease when pH decreases. The reason is that at low pH, the zeta potential and the partition coefficient both decrease, corresponding to a smaller charge density at the mineral surface, resulting in a weaker impact of the electrical double layer. The few existing experimental studies on pH dependence are qualitatively consistent with our simulation results.

This paper derives the Airborne Induced Polarization (AIP) response of an airborne electromagnetic (AEM) system to a horizontal, thin sheet conductor. A vertical component double-dipole approximates helicopter systems with towed concentric horizontal transmitter and receiver loops in frequency- or time-domain. In time domain, the AIP effect typically shows up as late-time negative data with amplitude 4 to 5 orders of magnitude smaller than the early-time peak of the positive AEM responses. Because of limited bandwidth from the short sample time after the decay of inductive responses, accurate extraction of intrinsic AIP parameters other than a minimum chargeability is almost impossible. Modelling further suggests that AIP effects in double-dipole AEM systems can only be reliably detected from polarizable material in the top few tens of metres. A titanium mineral exploration case history from the Lac Brule area, Quebec, Canada illustrates strong spatial coherence of AIP minimum chargeability estimates and their independence from other effects such as conductivity and magnetic susceptibility.

Multiferroic materials with such magnetoelectric properties that are comparable to the useful ferroelectrics and ferromagnets are exceedingly rare. We report here on integration of ferroelectricity and ferromagnetism in a M-hexaferrite (La 0.2 Pb 0.7 Fe 12 O 19 ), which simultaneously exhibits colossal magnetocapacitance effect at room temperature. The coexistence of the off-centered FeO 6 octahedron and electron spins in partially filled Fe 3d or La 3f orbits is supposed to be responsible for mergence of mutually exclusive electric and magnetic orders. Five magnetoelectric phases and boundaries have been built up by the permeability profile. By applying a magnetic field (B), the capacity or dielectric constant demonstrates giant oscillations, whose maximum amplitude exceeds 1.90 × 10 5 % at 80 Hz. The huge oscillations are associated with the variable component and orientation of the cycloid conic spins at the boundaries between two neighboring magnetic phases, where the cycloid cone axes align themselves parallel or reversal parallel to the direction of B field. Thus the dielectric constants are systematically enhanced to reach a giant value of e m ± ′ = +58270 or −84866 due to the great promotion of spin-current induced polarization.

Robust ferroelectric films, which are universally associated with defects, require a standard rectangular polarization hysteresis loop to be viable in technological applications. We demonstrate that the polarization of the PbTiO 3 –Bi(Mg 1/2 Ti 1/2 )O 3 based ferroelectric thin films is unusually waked up, and a standard hysteresis loop is obtained. It is first time to directly observe the reorientation of domain fractions by high-resolution synchrotron x-ray diffraction which is the origin of the polarization wake-up, simultaneously corresponding to the piezoresponse force microscopy measurements. The polarization rejuvenation can also be systematically controlled by the poling cycles and defect concentration, which is related to defect rearrangement. The present work provides a picture to understand the physics of defect activity and domain evolution in ferroelectric thin films, facilitating the optimization of the ferroelectric for applications which require a stable polarization.

This work exploits the dissipaton equation of motion (DEOM) approach to study the solvent-induced non-Condon polarization dynamics and its two-dimensional coherent spectroscopy for model excitonic systems. DEOM is a second quantization generation of the celebrated hierarchical equations of motion theory, with the capability of accurate evaluation for both reduced system and hybrid bath dynamics. The underlying dissipaton algebra includes the generalized Wick’s theorem and DEOM-space techniques for hybrid bath dynamics. Methods discussed also involve an efficient derivative–resum level truncation scheme that preserves the prescription invariance, and the mixed Heisenberg–Schrodinger picture approach for efficient simulation of nonlinear response functions. Our model simulations show clearly the correlated system-and-bath interference and the resulting Fano entanglement spectroscopy profiles.

Due to the increasing demand for some metals the investigation of abandoned mine waste dumps for the potential reuse of ore mining residues becomes more important. This study examines the suitability of the spectral induced polarization (SIP) method to distinguish different ores in the mine dumps and evaluate the deposited amounts. We investigated SIP characteristics of four sulphides: pyrite (FeS 2 ), chalcopyrite (CuFeS 2 ), galena (PbS) and sphalerite (ZnS). Laboratory measurements on fully saturated synthetic ore-sand-mixtures (FeS 2 , PbS, ZnS) with three different grain radii (between 31 μ m and 500 μ m), three different ore concentrations (0.5 vol.-%, 2 vol.-%, 6 vol.-%) and with different electrical conductivities of the pore fluid (between 25 mS/m and 400 mS/m, sodium chloride) for pyrite- and chalcopyrite-sand mixtures have been carried out. A new four-point sample holder for precise and reproducible measurements of the unconsolidated mineral-sand mixtures has been developed. The measurements were done at constant temperature of 20 ∘ C within a frequency range from 1 mHz to 45 kHz using a high-accuracy impedance spectrometer. Several trends for the induced polarization signature have been observed. First, the polarization signal increases with higher ore mineral content. Second, both phase amplitude and peak frequency increase with decreasing grain radius. Third, the frequency of the phase maximum is shifted to higher values for increasing fluid conductivity. Fourth, all ores showed similar phase characteristics, solely sphalerite indicated lower phase magnitude. By fitting the IP spectra on basis of a Cole–Cole model, the parameters chargeability ( m ) and time constant ( τ ) have been derived. The following relations were confirmed: 1) chargeability rises with increasing ore mineral concentration. 2) The time constant increases with increasing grain radius. Ore-specific quantities are determined by these relations. The results show that conclusions about the ore mineral content, grain radius and fluid conductivity can be derived from laboratory SIP measurements. The method seems to be suitable to identify sulphide minerals in sandy mixtures but a differentiation between the different types of ore minerals remains a challenging task. Nevertheless, more investigations are required to improve the reliability of these findings towards a field scale application.

Abandoned mining waste dumps may become potential resources for mineral reuse. For evaluating such structures, their spatial extension, the mineral content and predominating grain size needs to be determined. Amongst geophysical prospection methods, induced polarization (IP) is particularly suited since ore minerals show significant polarization characteristics. From laboratory measurements it is known that there is a relation between mineral concentration and chargeability, whereas the frequency content is mainly dominated by grain size. Spectral IP (SIP) field data using a range of measuring frequencies can potentially map these quantities spatially. Instead of inverting the individual frequencies independently, we introduce a scheme where adjacent frequencies are constrained to each other. We test it using a synthetic model based on the Cole–Cole model with a body containing two parts of differing time constants. The inversion approach is able to reliably recover the Cole–Cole parameters. We apply the method to a field data set from a slag dump containing melting residuals from different minerals. The resulting models exhibit distinct zones of decreased conductivity and increased polarization that are not fully coincident. Furthermore, we observe a significant change in the spectral content. Taking into account recent laboratory investigations, the obtained chargeabilities hint to the occurrence of sufficient mineral concentration. In comparison with direct current resistivity, there is a clear benefit from using SIP field data in general and spectral analysis in particular.

The shallow ( induced polarization (IP) to map details of bedrock and soil sediments. The bedrock is mostly comprised of limestone, and is generally resistive compared to the overlying soil. The soil-bedrock interface was determined through a trial and error approach using a sharp boundary feature in the inversion model. The inferred bedrock surface determined from the inversions exhibited undulating patterns with troughs and ridges. A near continuous trough ran alongside the stream within the floodplain, and is suggestive of a paleochannel among other interpretations of this feature. The structure of the electrical resistivity above the bedrock showed small-scale elongated features. The chargeability from the IP method showed larger scale features. High values of chargeability were associated with the sediments in the floodplain, and low values were associated with bedrock, stream, and soil on the elevated banks above the stream. If the chargeability is associated with membrane polarization characteristic of clayey soils, then IP seems to highlight the mere existence of clay, while the resistivity may be more discernable of the relative proportion of clay. Vegetation differences may also explain the chargeability distribution, where parts of the survey with high chargeability had dense pine with no understory making the soils more organically rich.

Induced Polarization (IP) surveys are commonly used to visualize the physical property of chargeability and are a widely applied tool to investigate subsurface geological structure . In this work we explore the petrological control on chargeability to better understand the underlying geological features that IP surveys may image. We report the results of petrophysics, automated mineralogy , and image analysis from a case study of eleven samples from the Salmon Canyon cobalt‑copper deposit in Idaho, USA with the aim of enhancing comprehension of the relationship between mineralogy and petrophysics. While total sulphide volume is positively related to chargeability, total number of sulphide grains and chargeability have a significantly stronger association. Of the sulphide minerals present in these samples, chalcopyrite is the predominant influence on chargeability response, followed by pyrite, while cobalt-bearing sulphides appear disassociated with response. Specifically, chalcopyrite grains less than 200 μm diameter yield the greatest association to chargeability while grain sizes larger than 200 μm have an association that is notably less significant. Grain shape parameters were examined for potential causation to this grain size drop in chargeability but do not yield any distinct relationship. However, chalcopyrite grain characteristics do exhibit strong correlations with the metamorphic minerals stilpnomelane and tourmaline , implying that chalcopyrite grain abundance and shape are modified during metamorphism . A strong relationship between the presence of stilpnomelane and total number of chalcopyrite grains implies that the process of stilpnomelane growth during metamorphism leads to enhanced conductive ore dissemination and hence chargeability. Furthermore, tourmaline presence correlates with chalcopyrite grain abundance and specifically greater tourmaline is linked with more elongate (less round) large chalcopyrite grains. The results of this case study implies that IP in part images metamorphic processes.