Search

A magnetocaloric effect with wide tunability was observed in melt-spun amorphous Gd65Fe15-xCo5+xAl10Si5 (x = 0, 5, 10) alloys of different Fe/Co ratios. Their magnetic properties were compared with those of the previously investigated parent alloy Gd65Fe10Co10Al15. The glassy structure of the melt-spun samples was confirmed by X-ray diffraction (XRD) and 57Fe Mössbauer spectrometry. Their Curie temperatures (TC) were between 155 and 195 K and increased significantly with decreasing Co content. The highest value of the magnetic entropy change ΔSM = − 6.8 J/kg K was obtained for Gd65Fe5Co15Al10Si5, when the magnetic field was increased from 0 to 5 T. Refrigerant capacity (RC) takes values close to 700 J/kg for the whole series of the alloys. The occurrence of the second-order phase transition and the conformity of the magnetic behavior with the mean field model were concluded on the basis of the analysis of the universal curves and the values of the exponent n (ΔSM ∝ Hn). Graphical abstract

The conversion of metal-modified (Fe, Co) sawdust into magneto-sensitive porous composites using thermal carbonization process in an inert atmosphere was successfully achieved. The as-prepared samples were characterized using nitrogen adsorption, X-ray diffraction, scanning electron microscopy and thermal analysis methods. The obtained results show that the structural and morphological characteristics of the obtained composites depend strongly on the metal precursor’s types. All samples exhibited a good magnetic property and can be easily separated from liquids by an external magnet.

The structural and magnetic properties of Fe/Fe3O4 nanocomposites, synthesized by combined high energy ball milling and controlled oxidation, have been studied. An X-ray diffraction analysis of the crystal structure of the nanocomposites confirmed the coexistence of Fe and Fe3O4 phases. An increase of the oxygen concentration during oxidation process led to the formation of a higher fraction of the Fe3O4 phase with good crystallinity and stoichiometry. The morphology of the nanocomposites revealed a lamella-like structure with a thickness of about 30 nm. The saturation magnetization decreased when the phase fraction of Fe3O4 increased. The coercivity was enhanced at low temperatures (≤100 K) but decreased at high temperatures, due to thermal fluctuation effects on the anisotropy in the Fe3O4 phase. Interestingly, the lamellae exhibited a sharp Verwey transition near 120 K, which is often suppressed or absent in nanostructured Fe3O4 due to the poorly crystalline, off-stoichiometric characteristic. The temperature dependence of high-field magnetization of the lamellae is analyzed by the modified Bloch law. Our study demonstrates the possibility of tuning the magnetism in iron/iron oxide nanosystems through controlled oxidation.

Attaining robust magnetic long-range order in ferroelectric Aurivillius-phase oxides at room temperature has recently attracted considerable attention of materials scientists and engineers for the development of magnetoelectric-active materials in microelectronics and spintronics. Here, we report the structural evolution and its relation to the macroscopic magnetization of a series of samples of Aurivillius (Bi4.3Gd0.7)(Fe1−xCox)1+yTi3−2yNbyO15 (x = 0, 0.3, 0.5 and y = 0, 0.3) compounds prepared by a solid state reaction, aiming at shedding light on the Co substitution-induced ferromagnetism at room temperature and above. The Co-free composition showed a single-phase four-layered Aurivillius structure (space group A21am), while the Co substitution was found to give rise to a mixed-layer structure composed of four- and three-layered phases. Rietveld analysis of the synchrotron X-ray diffraction data showed that the reduction in the number of layers across the Aurivillius morphotropic transition boundary is accompanied by a structural phase transformation from A21am to B2cb. The disordered intergrowth of these phases was evidenced by high-resolution transmission electron microscopy and found to originate from a nanoscale structural modulation occurring at the interface between the two phases. A sextet suggesting long-range magnetic ordering in the doped samples was deduced from Mossbauer spectra. Magnetic-property measurements, indeed, confirmed a ferromagnetic state of these samples at elevated temperatures. The highest values of the remanent and saturation magnetization at room temperature were obtained for the compositions with x = 0.3, in which the occurrence and enhancement of the magnetization can be attributed to the ferromagnetic clustering of the FeO6 and CoO6 octahedra and, partly, also to spin canting effects and/or a double-exchange magnetic interaction between the mixed valence cobalt through oxygen. The cooperative freezing of randomly distributed Fe–O–Co clusters is suggested to be responsible for the spin glass-like behaviour observed at low temperatures. The occurrence and enhancement of the magnetization in the ferroelectric Co-doped Aurivillius ceramics are attributed, respectively, to the structural modulation and the population of the ferromagnetic clusters near the interface of the four- and three-layered phases.

Study of the interlayer interactions and hysteresis processes was performed for the nano/microcrystalline bilayer ribbon composed of soft magnetic Fe73.5Cu1Nb3Si13.5B9 layer and semihard magnetic Co72.5Si12.5B15 layer. Precursor amorphous ribbons were prepared by modified double-nozzle planar flow casting method. Measurement of the First Order Reversal Curves (FORCs) was utilized for detailed characterization of its magnetic hysteresis behaviour. Calculated switching field distribution (SFD) consists of two distinct peaks, each representing specific magnetic phase. With decreasing reversal field value, SFD peak of the microcrystalline, semihard magnetic Co-based layer is shifted to the higher field values, indicating presence of strong positive exchange interaction. On the other hand, SFD peak of the soft magnetic nanocrystalline Fe-based layer is shifted to lower and even negative field values. Such behaviour was associated with the presence of magnetostatic bias field originating in the semihard magnetic layer.

Co-CoO composite powders were prepared by high-energy ball milling and subsequent annealing with the aim to probe an exchange bias (EB) effect. A microstructure consisting of flakes with a thickness of about 100 nm was revealed from scanning electron microscopy images. X-ray diffraction phase identification indicated that the optimal annealing temperature of as-milled Co for the formation of Co-CoO composite structure is 300°C. Magnetic measurements showed that saturation magnetization, Ms, of annealed Co-CoO decreased as compared to that of as-milled Co. This implies that a fraction of the oxide phase was formed after heat treatment. Furthermore, the hysteresis loop measured at 5 K after cooling in a magnetic field of 50 kOe from 350 K showed a presence of the EB effect, which reached the value of 120 Oe. It is closely related to the formation of an antiferromagnetic (AFM) CoO phase, which interacts with the adjacent Co ferromagnetic (FM) phase. A Monte-Carlo simulation was also performed to demonstrate the EB effect in FM–AFM structured materials. A better agreement between simulated and experimental hysteresis loops was obtained when averaged characteristics of the randomly-oriented individual powders were taken into account. Simulation results also showed that EB is largest when easy axes of FM and AFM phases are parallel to the magnetic field, and a critical fraction of AFM phase was suggested to be necessary for appearance of the EB effect.

Impact of rapid annealing on the soft magnetic properties of the Fe80Nb3Cu1Si6B10 alloy has been investigated. Parent as-quenched ribbons were prepared by planar flow casting method. Rapid thermal treatments (7-30s) has been conducted at 500°C using the preheated Cu blocks to ensure elevated heating rate of more than 100 K/s. Reference samples were isothermally annealed in the vacuum furnace for 1 h at the same temperature. X-Ray diffraction unveiled formation of nanocrystalline structure of bcc α-Fe(Si) grains, embedded in the residual amorphous matrix in all processed samples, irrespective of the annealing technique. Evolution of coercivity and saturation magnetization values, obtained from the measured hysteresis loops, showed improved magnetic softness of the rapidly annealed samples, compared to the as-quenched and conventionally processed ones. Significant embrittlement of the samples after nanocrystallization has been observed regardless of annealing time and thermal treatment technique used.

We demonstrate the use of elemental precursors Cu, Fe, Sn, and S to obtain a mawsonite (Cu6Fe2SnS8)/stannite (Cu2FeSnS4) composite using a solid-state process at ambient temperature in an industrial eccentric vibration mill for up to 240 min in argon atmosphere. The samples were characterized using various analytical techniques such as x-ray diffractometry, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and nitrogen adsorption and magnetic measurements. For thermoelectric measurements, the properties of samples densified via spark plasma sintering were measured using standard methods needed to calculate the figure of merit. The transformation of elemental precursors to a composite mixture proceeds relatively rapidly via several intermediate steps. The kinetics of this transformation is also in good agreement with the results for the unconsumed sulfur content in the reaction mixtures and can also be correlated with the magnetization results. Based on the thermoelectric measurements of the sample milled for 240 min, the calculated figure of merit reached a value of zT = 0.51 at 623 K due to a very low lattice thermal conductivity of 0.29 W/m-K and moderate power factor of 3.3 μW/cm-K2. The thermoelectric results obtained for the material are comparable to previously published values for pure mawsonite prepared from elements by laboratory ball milling.

The rapid mechanochemical synthesis of nanocrystalline CuFeS particles prepared by high-energy milling for 60 min in a planetary mill from copper, iron and sulphur elements is reported. The CuFeS nanoparticles crystallize in tetragonal structure with mean crystallite size of about 38 ± 1 nm determined by XRD analysis. HRTEM study also revealed the presence of nanocrystals with the size of 5–30 nm with the tendency to form agglomerates. The Raman spectrum confirms the chalcopyrite structure. Low temperature magnetic data for CuFeS support the coexistence of antiferromagnetic and paramagnetic spin structure. Moreover, the hysteresis loops taken at temperatures from 5 K to 300 K revealed a presence of very small amount of ferromagnetic phase, which seems to be associated with the non-consumed elemental Fe in as-prepared nanoparticles. The optical band gap of CuFeS nanoparticles has been detected to be 1.05 eV, larger than band gap of the bulk material. The wider gap possibly resulted from the nano-size effect. Photoresponses of CuFeS nanoparticles were confirmed by I-V measurements under dark and light illumination. It was demonstrated that mechanochemical synthesis can be successfully employed in the one step preparation of nanocrystalline CuFeS with good structural, magnetic, optical and electrooptical properties., This work was promoted by the Slovak Research and Development Agency under the contract No. APVV-14-0103. The support through the Slovak Grant Agency VEGA (projects 2/0027/14, 1/0739/16 and 2/0065/18) is also thankfully acknowledged. The authors also appreciate the help of the European Regional Development Fund- project NANOCEXMAT 2 (ITMS 26220120035) and European Union through the CT-2011-1-REGPOT285895 AL-NANOFUN project (Advanced Laboratory for the Nano-Analysis of novel Functional materials), for the microscopy facilities sited in Seville.

Aurivillius-phase ferroelectrics can be turned into multiferroic materials by incorporating magnetic ions. The four-layer Aurivillius-type system Bi5FeTi3O15 is well-known to show a strong magnetoelectric effect; however, much controversy exists on its magnetic state and the possible multiferroicity at room temperature. In this paper, we report a detailed investigation on the interconnections between crystal chemistry and magnetic properties of Bi5FeTi3O15 ceramics chemically modified by the A-site gadolinium substitution. The structural studies showed that all Bi5–xGdxFeTi3O15 (0 ≤ x ≤ 1) samples adopt the polar orthorhombic space group symmetry A21am at room temperature. The unit cell volume and the orthorhombic distortion decrease alongside the reduction of octahedral tilts by increasing the amount of Gd added. The decrease in tilting distortion of the [Ti/Fe]O6 octahedra was further evidenced by the suppression of the Raman A1[111] tilt mode at 233 cm–1. By using superconducting quantum interference a...

In this study, the mechanochemical synthesis of Co9S8 nanoparticles from cobalt and sulphur by high-energy milling in a planetary mill in an argon atmosphere is reported. Structural characterization of the synthesized nanoparticles by XRD was performed. Co9S8 nanoparticles crystallize in the cubic structure with the crystallite size of about 16 nm. The microstructure of the Co9S8 nanoparticles was further studied using TEM, HRTEM and EDS-HAADF-STEM techniques. Co9S8 nanoparticles consist of nanocrystals exhibiting size in the range of 10–30 nm that are densely aggregated into spherical-like objects. The highest specific surface area value observed was 4 m2g-1 and the pore properties of this sample are quite poor. The magnetic properties of mechanochemically synthesized nanoparticles were investigated using SQUID magnetometer. The room temperature magnetic data supported the paramagnetic spin structure of Co9S8 nanoparticles. The transition from paramagnetic to weak ferromagnetic or ferrimagnetic behaviour was indicated from temperature dependence of magnetization at cryogenic temperatures. It is demonstrated that mechanochemical synthesis can be successfully employed in the one-step solid-state preparation of Co9S8 nanoparticles.

There is a pressing need for improving the high-frequency magneto-impedance (MI) response of cost-effective soft magnetic materials for use in high-performance sensing devices. We report here a comparative study of uncoated (Fe50Ni50)81Nb7B12 nanocrystalline ribbons and ribbons coated with 120 nm of Co on both surfaces. The impact of the Co coating on the high frequency impedance of the (Fe50Ni50)81Nb7B12 ribbon was studied with techniques sensitive to surface magnetism, namely magneto-optical Kerr effect (MOKE), MOKE microscopy, and high frequency impedance as a function of magnetic field. MOKE microscopy on the coated ribbons showed a superposition of high anisotropy domains from the crystalline Co and wide magnetic domains from (Fe50Ni50)81Nb7B12. In full agreement with the MOKE results, MI measurements indicated an increase in anisotropy field in the excitation frequency range 100–1000 MHz in the Co-coated ribbons. Noticeably, the Co-coating improved the MI ratio by 15% at fields near and below the anisotropy field. The improvement of the low-field MI response by the coating encourages the use of magnetic coatings to improve MI-based sensors in ribbon geometry for technological applications such as biomagnetic sensing. This study also yields insights into the effects of negative magnetostrictive coatings on the MI behavior in soft magnetic ribbons.

The criminalization of offensive, privacy-intrusive behavior is an important form of privacy protection. However, few studies exist of visual observation in criminal law. We address this gap by researching when nonconsensual visual observation is deemed harmful enough to trigger criminal sanctions, and on what basis the law construes the “reasonableness of remaining unobserved,” through a nine-country comparative study. We distinguish between voyeurism-centric approaches (focusing largely on nudity and sex) and broader, intrusion-centric approaches (such as observation inside closed spaces). Both approaches explicitly or implicitly reflect “reasonable” privacy expectations, listing criteria for situations in which people can reasonably expect to remain unobserved or unrecorded. We present a framework for criminalizing nonconsensual visual observation, encompassing factors of technology use, place, subject matter, and surreptitiousness, supplemented by factors of intent, identifiability, and counter-indicators to prevent over-criminalization. This framework is relevant for protecting visual aspects of privacy in view of individuals' underlying autonomy interests.

The influence of Ce addition on the nature of phase transition in the La1−x Ce x Fe11.2Co0.7Si1.1 (x = 0, 0.1) alloy system has been investigated. The substitution of Ce for La leads to a decrease of Curie temperature from 264 K to 254 K and to an increase of the maximum value of magnetic entropy change from 19.3 J/(kg K) to 21.5 J/(kg K). A detailed analysis of phase transition using Arrott plots, the Landau theory for order parameter and the construction of a universal scaling curve revealed that replacing 10 at.% La with Ce drives the magnetic transition from second-order to first-order and enhances a field-induced itinerant electron metamagnetic transition above T C.

Partial substitution of isovalent rare-earth ions for bismuth is one of the most effective ways to develop room temperature BiFeO3-based multiferroic materials with high resistivity and strong magnetoelectric coupling. However, their structures and properties are composition and processing sensitive, with the underlying mechanisms still far from being completely understood. Here we report on the structural, thermal and magnetic properties of polycrystalline Bi1−xTbxFeO3 (0 ≤ x ≤ 0.30) dense ceramics prepared by spark plasma sintering (SPS). The X-ray diffraction study reveals that increasing terbium content induces a structural transformation from the parental rhombohedral (R3c) polar phase to an orthorhombic (Pnma) non-polar phase at x ≈ 0.20–0.25. Complementary Raman and energy-loss near-edge structure (ELNES) spectroscopy studies indicate that the transition proceeds by the progressive loss of Bi–O hybridization. Suppression of the long-range ferroelectric ordering upon Tb substitution and loss of ferroelectricity at x ≥ 0.25 was also confirmed by differential scanning calorimetry. High-sensitivity magnetic measurements show that the introduction of a small amount of Tb3+ ions at the A-sites of the perovskite structure gives rise to the occurrence of spontaneous magnetization at room temperature. The reduced degree of Fe 3d–4p orbital mixing and the weaker Fe 3d–O 2p hybridization, revealed by ELNES and X-ray near-edge absorption fine structure (NEXAFS) analyses, suggest that the substitution-induced changes in the electronic structure are responsible for the enhanced magnetization in Tb-doped BiFeO3. Among the biphasic (R3c + Pnma) compositions with ferroelectric order, the Bi0.8Tb0.2FeO3 compound shows the highest value of remanent magnetization (Mr ≈ 0.26 emu g−1), which makes this material a potential candidate for magnetoelectric applications.

In this study, we suggest an alternative design of the fluxgate sensors at race-track geometry. We have investigated the influence of the number of core layers on the sensor performance by making sensitivity and noise measurements. With this purpose, we have prepared four sensors which all have the same characteristics but consist of one, two, three and five layers of the magnetic ribbons. After finding the optimal number of core layers, optimization works were carried out on that sensor. We have finally achieved to get a sensitivity of ∼166 kV/T and a noise level of 18 pT/√Hz@1Hz respectively.In this study, we suggest an alternative design of the fluxgate sensors at race-track geometry. We have investigated the influence of the number of core layers on the sensor performance by making sensitivity and noise measurements. With this purpose, we have prepared four sensors which all have the same characteristics but consist of one, two, three and five layers of the magnetic ribbons. After finding the optimal number of core layers, optimization works were carried out on that sensor. We have finally achieved to get a sensitivity of ∼166 kV/T and a noise level of 18 pT/√Hz@1Hz respectively.

This paper analyses the implications of a new form of surveillance—sewage monitoring—for criminal procedural law. Current law has not been written with a view to covering novel, technology-enabled forms of covert data acquisition, posing a challenge of regulatory connection. To what extent are new surveillance methods, such as sewage monitoring to combat drugs production, covered by existing legal frameworks? This question is answered through analysing the shifting nature of criminal investigation, reflecting on how to interpret laws not written for new technologies, and assessing checks and balances needed when law enforcement employ sewage monitoring in criminal investigation. The analysis is illustrated with reference to the legal systems of Germany, Poland, and the Netherlands, using legal doctrinal research. The main findings are 1) that sewage monitoring is not particularly intrusive as such, but constitutes a new form of investigation that legally differs significantly from traditional surveillance powers, 2) that comparable methods do not provide unequivocal analogies that could serve to find a legal basis, 3) that functionality of evidence collection poses legal and procedural challenges, which may have implications for the covertness of the method, and 4) that even if only used as a diagnostic tool, some form of transparency and oversight will be needed to legitimate the non-negligible potential interference with fundamental rights and to enable those subjected to sewage monitoring to contest the usage in court.

The fundamental right to inviolability of the home has traditionally been interpreted to protect people from physical intrusions into their homes. The growing use of technologies for non-physical intrusion into the home, enabling surveillance from the outside by law enforcement, makes home life more transparent without investigating officers having to physically enter. Sewage monitoring is an emerging new form of surveillance of the home from the outside, which potentially impacts the level of protection of home life in practice and in the law. The purpose of this paper is to survey forms of surveillance of the home similar to sewage monitoring, describe how German, Polish and Dutch law regulate these forms of surveillance, and suggest improvements to the legal framework so that people’s fundamental right to protection of their home life remains sufficiently safeguarded. We group surveillance of the home from the outside into five groups: waste monitoring, monitoring of emanations, audio-visual surveillance, access to data in the home, and out-of-home access to data about home life. Our analysis shows that visual surveillance, acoustic surveillance, and access to data in and about the home are relatively well-regulated, usually with a sufficiently clear legal basis and considerable safeguards, thus offering generally adequate legal protection. In contrast, regulation of domestic waste (garbage and sewage) monitoring and monitoring of emanations from the home (heat, smell, electromagnetic waves) is less clear. Although these surveillance measures seem less serious interferences with inviolability of the home, law-makers should clarify the legal basis for these methods and the conditions applying to them. We conclude that legal systems will need to develop ways to more clearly distinguish between minor, more than minor, and very serious interferences with inviolability of the home. The Dutch systematicness requirement and the German protection of the core area of private life are useful starting points for developing a more comprehensive normative framework that can deal with non-physical intrusions of the home as well as current legal frameworks regulate physical intrusions of the home.

(Fe65Co35)83.5−xB13NbxSi2Cu1.5 amorphous ribbons with (4 at.%) and without (0 at.%) growth inhibitor Nb were Joule annealed at low current intensity to avoid bulk crystallization, and their surface domain structure, bulk and surface magnetization, and high frequency magneto-impedance (MI) were systematically investigated. Magneto-optic Kerr effect (MOKE) microscopy and longitudinal MOKE evidenced the development of a longitudinal surface anisotropy in the ribbon without Nb (Nb0) as a result of the Joule annealing treatment, while the 4 at.% Nb (Nb4) ribbon developed an anisotropy 30° from the transverse direction. The increased transverse ac permeability at the surface of Nb4 was evident in MI measurements by a higher [ΔZ/Z]max as compared to Nb0 at frequencies greater than 200 MHz. A correlation between the surface domain structure, induced anisotropy and high frequency MI in the ribbons was established.

Evolution of crystalline structure caused by heat treatment and its influence on magnetic properties of two melt-spun Hf2Co11B alloys in fully amorphous and partially crystalline states have been investigated. The as-cast ribbons were annealed in order to improve the hard magnetic properties by inducing the formation of nanocrystalline phases with high anisotropy. The X-ray diffraction and magnetic measurements confirmed the coexistence of two Hf2Co11 phases, crystallizing in different structures, with the rhombohedral one showing hard magnetic properties. Annealing of fully amorphous alloy resulted in the lower coercive field in comparison to that of annealed partially crystalline ribbon. From the point of view of exchange coupling between magnetic phases and magnetic hardening, the optimum annealing temperature and time were determined to be 570 °C and 60 min, for partially crystalline sample. Annealing at 650 °C for 1 h leads to excess of the HfCo3B2 phase above the critical value and results in a decrease in the coercive field. Isothermal annealing increases the magnetocrystalline anisotropy constant K1 from 7.52 for the as-quenched sample to 12.11 Merg/cm3 for the partially crystalline ribbon. The existence of quenched-in nanocrystals resulted in higher coercive fields, up to 3.23 kOe, after annealing.

The magnetic anisotropy field distribution is discussed for Hitperm alloys annealed under different field conditions leading to different induced magnetic anisotropies: zero (ZF), transversal (TF), and longitudinal (LF) field annealing and compared to that of as-quenched (AQ) melt-spun amorphous ribbon. In order to accurately use the present method, the demagnetizing factor has been obtained by analyzing the field dependence of the inverse of the field derivative of the magnetization. The coherence of the analysis is supported by testing the normalization of the complete distribution of anisotropy fields. Independently of the composition, two groups can be distinguished among the studied samples: those with mainly perpendicular anisotropy field contributions (ZF and TF samples) and those with mainly longitudinal anisotropy field contributions (LF and AQ samples). Behavior of TF samples is well reproduced using Stoner-Wohlfarth model and, in the case of as-quenched amorphous samples, the anisotropy field depends almost linearly on the thickness of the ribbon., Work supported by the Spanish MINECO and EU FEDER (Project MAT 2013-45165-P), the PAI of the Regional Government of Andalucía and the Slovak projects APVV-0492-11, VEGA 2/0192/13. The Slovak team acknowledges also the support of the Operational Program “Research and Development” financed through European Regional Development Fund through the projects ITMS 26220120019 and ITMS 26220220061.

A comparative study was performed on the mechanical and giant magneto-impedance (GMI) properties in the longitudinal and transverse directions of Co69Fe4Ni1Mo2B12Si12 amorphous ribbons. Both mechanical and GMI properties were found to be anisotropic. Kerr microscopy shows the presence of a stripe-type domain structure with the magnetic easy axis parallel to the longitudinal direction. The fracture strength, elastic modulus, and fracture toughness in the transverse direction was higher than those in the longitudinal direction. A larger GMI response was achieved in the transverse direction at a frequency range where both the domain wall motion and spin rotation dominantly contributed to the effective permeability and hence the magneto-impedance. The current study paves the way for designing Co-rich amorphous ribbons as desirable components in electronics such as magnetic sensors.

Compared to other sensors, such as radio-frequency identification sensors, microwires have a significant advantage due to their small dimensions and contact-free reading. The most important advantage is that a microwire is considered to be a biocompatible material due to the glass-coating insulator. This is particularly applicable in various titanium implants (dental, knee joint, replacement of damaged skull part, repair of the femur, etc.). The temperature dependence of the switching field can be employed to monitor inflammatory processes. In this contribution we present the influence of molybdenum (Mo) content on the magnetic properties and thermal treatment in order to obtain a strong variation of the switching field to temperature. We show that stress annealing of a FeMo9BCu microwire at 775 K under an applied axial stress of 309 MPa leads to the strongest variation in a temperature range from 300 to 315 K, which is highly desirable for biomedical applications.

We have recently applied the magnetic field and temperature dependence of magnetic entropy change as a probe of the magnetic states of a single crystal of Ca3Co2O6 to establish a more comprehensive magnetic phase diagram for this exotic system. The results are consistent with the spin-density wave description of the ground state and indicate the suppression of the modulated state in favor of a ferrimagnetic up-up-down arrangement of the spin chains with the application of a moderate field. We demonstrate, in this study, that the features of the static magnetic phase diagram are preserved when the grain size of Ca3Co2O6 is reduced to 440 nm (below the maximum c-axis correlation length of ~550 nm in Ca3Co2O6), although the polycrystalline materials show a non-saturating behavior, rounded steps, and reduced magnetization when compared to the single crystal. Our new finding of the multiple low-temperature magnetization steps in the 440 nm sample, together with conflicting reports concerning such steps in nanostructured samples, suggests that correlations in the ab plane are more important than correlations along the c-axis in the appearance of the plateaus. The relaxation processes in the system are studied through the decay of remanent magnetization, ac susceptibility, and Argand diagrams. The introduction of grain boundaries in Ca3Co2O6 weakens the slow-dynamic state, widens the low-temperature distribution of relaxation times, and lowers activation energies within the Arrhenius-like relaxation regime.

In this work, we report on the magnetic and dielectric anomalies observed in dense Bi1–xRExFeO3 ceramics (RE = Dy, Tb; 0 ≤ x ≤ 0.3) at cryogenic temperatures. For compositions with a high content of rare-earth ions, thermomagnetic experiments revealed a distinct anomaly in the magnetization curves at temperatures below 200 K. The temperature of the magnetic anomaly along with a thermal hysteresis was found to be dependent on the rare-earth concentration and magnetic field strength. Low-temperature dielectric measurements showed an anomalous relaxor-like behavior of the relative permittivity and dielectric loss in highly doped ceramic samples. The anomalies in low-temperature magnetization and dielectric response are suggested to result from the presence of GdFeO3-like orthoferrite phase and/or bismuth rare-earth-mixed iron garnet impurities.

This report researches civil law remedies to combat cybercrime. Using the instrument of duties of care and diligence (spanning tort law and contract law), several actors might be motivated to take additional care in acting in ways that diminish possibilities for cybercrime. The study is based on Dutch law, US law, Czech law, and Brazilian law. The report focuses on software vendors, businesses, and Internet Service Providers.

Proceedings of the 16th Czech and Slovak Conference on Magnetism, Košice, Slovakia, 13 Jun 2016 - 17 Jun 2016; Acta physica Polonica / A 131(4), 747 - 749 (2017). doi:10.12693/APhysPolA.131.747, The influence of precipitation temperature on structural and magnetic properties of iron/iron-oxide nanoparticles is investigated. Nanoparticles were prepared by precipitation of$\gamma$-Fe precipitates in Cu–Fe solid solution and subsequently isolated by matrix dissolution. Precipitation annealing temperatures were 773, 873, and 973 K. Nano- particles core-shell structure and morphology were characterized by X-ray diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction. These measurements showed that average diameter of nanoparticles increases with precipitation temperature from 8.5 nm to 20.5 nm. The measurements of magnetization as a function of temperature and applied field have been performed by SQUID magnetometer in temperature range from 5 K to 200 K., Published by Acad. Inst., Warsaw

In this study, we demonstrate a one-pot mechanochemical synthesis of the nanocomposite composed of stannite Cu2FeSnS4 and rhodostannite Cu2FeSn3S8 nanocrystals using a planetary ball mill and elemental precursors (Cu, Fe, Sn, S). By this approach, unique nanostructures with interesting properties can be obtained. Methods of XRD, Raman spectroscopy, UV-Vis, nitrogen adsorption, SEM, EDX, HRTEM, STEM, and SQUID magnetometry were applied. Quaternary tetragonal phases of stannite and rhodostannite with crystallite sizes 18–19 nm were obtained. The dominant Raman peaks corresponding to the tetragonal stannite structure corresponding to A-symmetry optical modes were identified in the spectra. The bandgap 1.25 eV calculated from UV-Vis absorption spectrum is very well-acceptable value for the application of the synthesized material. The SEM micrographs illustrate the clusters of particles in micron and submicron range. The formation of agglomerates is also illustrated on the TEM micrographs. Weak ferromagnetic properties of the synthesized nanocrystals were documented

Thermal processing of materials in external magnetic field is employed in order to produce a controllable uniaxial anisotropy and to tailor a domain structure in the series of soft magnetic FeCo-and FeNi-based amorphous/nanocrystalline alloys. Examples of our recent work on the utilization of both longitudinal and transverse magnetic field annealing for tuning the shape of hysteresis loops as well as the giant magnetoimpedance (GMI) characteristics are briefly presented. The beneficial effects of a heat treatment under magnetic field are discussed in terms of the improved application-oriented properties of these soft magnetic alloys.

The polycrystalline samples of multiferroic Bi 1− x Dy x FeO 3 ( x = 0, 0.1, and 0.2) were prepared by a modified solid state reaction method and characterized by X-ray diffraction, scanning electron microscopy, differential thermal analysis, dielectric and magnetic measurements. It was shown that the introduction of the Dy 3+ ions stabilizes the perovskite structure and improves phase purity. The coexistence of the rhombohedral and orthorhombic phases was found to exist within the investigated concentration range 0.1 ≤ x ≤ 0.2. The changes and anomalies observed in dielectric response over a wide frequency range were correlated with the structural evolution and the development in microstructure. The SQUID measurements of the field-dependent magnetization at different temperatures demonstrated Dy doping to be a very effective method for inducing a weakly ferromagnetic state in the ferroelectric R 3 c phase of BiFeO 3 in the absence of an external magnetic field.

Glass forming abilities (GFA) of a ternary Y–Co–B system and its sub-binaries were calculated on the basis of semi-empirical Miedema’s and geometric models. Formation enthalpies of amorphous alloys, their solid solution counterparts and the differences between both were determined and discussed. As any additional alloying element promotes formation of glassy states, ternary alloys should be favored according to the empirical rules. However, in investigated ternary system atomic radius difference between Y and B is a deciding factor. Respectively, normalized mismatch entropy and glass forming ability parameter ΔPHS indicate the Y27B73 and Y35B65 compositions, as the best glass formers. Co-rich melt-spun RE–Co–B (RE = Y, Tb, Ho) ribbons with high GFA were prepared by rapid quenching to analyze their magnetic properties and the effect of rare earth element substitution on magnetic entropy changes. Magnetization vs. temperature curves indicate the ferromagnetic ordering in Y-containing alloy and sperimagnetic behavior for other amorphous alloys, due to the antiferromagnetic coupling between Co and rare earth element sublattices. Linear dependence of −ΔSm maxima on H2/3 is reported as a verification of second-order magnetic transition.

The ferromagnetic systems based on Fe-Sn-B, Co-Sn-B and Fe-Co-Sn-B were studied in nanocrystalline state due to their interesting magnetic properties that are caused by the homogeneous and ultrafine structure. The alloying of Co-B and/or Fe-B by Sn 3.5 and/or 5 at. % improves the properties of resulting structure composed of the ferromagnetic grains in the amorphous matrix as proved by the XRD and TEM methods. The structure transformation from amorphous to (nano)crystalline state was investigated by DSC and TGA methods and the resulting phase and morphology of crystalline products were analyzed.

Classical rapidly quenched nanocrystalline soft magnetic materials such as FINEMET, NANOPERM and HITPERM are seconded by new intensely investigated systems where special attention is put on materials with high saturation magnetization while preserving low coercivity. Diverse systems based on Fe-B with additions of Co, Cu, C, P and other elements were developed and tested. Successful compositional and processing design have lead to a new class of soft magnetic materials fulfilling these requirements based on Fe-Co-B, where the role of nanocrystal-forming element, namely nanograin size control, is taken up by Sn. Selected results will be presented on the case of rapidly quenched amorphous Fe-Sn-B alloy and its nanocrystallization by thermal treatment.

Gd-based amorphous alloys with addition of metals and metalloids are interesting materials from the point of view of magnetic and magnetocaloric properties. Moreover, they usually possess high corrosion resistance and good mechanical properties. A series of Gd 65 Fe 10 Co 10 Al 10 X 5 (X = Al, Si, B) alloys was synthesized by melt-spinning. The amorphous structure of ribbons was confirmed by X-ray diffraction. Calorimetric curves allowed to determine crystallization temperatures, which are in the range of 260°C-303°C. The temperature dependences of the magnetic entropy changes were calculated from series of isothermal magnetization curves using Maxwell relation. Maximum value of the magnetic entropy change for the magnetic field change from 0 to 5 T is 7.1 J kg -1 K -1 for X = B, whereas the related refrigerant capacity (RC) is 748 J kg -1 . For Gd 65 Fe 10 Co 10 Al 15 and Gd 65 Fe 10 Co 10 Al 10 Si 5 alloys, the maximum values of magnetic entropy change reached 6.0 and 5.9 J kg -1 K -1 , while the obtained values for RC parameter were 700 and 698 J kg -1 , respectively.

We report on novel approach for the abnormal growth of Goss grains that employs the system of VC nano-precipitates in combination with a phenomenon of the deformation induced grain growth. The laboratory slab of grain oriented steel was subjected to hot rolling with reduction of the thickness of sheet to 2.2 mm. The influence of coiling temperature on the distribution of VC particles was analyzed by TEM. The obtained results have confirmed the presence of VC nanoparticles with a typical size of 5-15 nm located preferentially in the vicinity of grain boundaries. Subsequently, the hot rolled strips were subjected to the cold rolling with the reduction e ~ 84%, followed by primary recrystallization, temper rolling and final annealing in dynamic conditions at 1050 °C. This procedure led to evolution of the sufficiently strong {110} 〈001〉 Goss texture, which follows in the soft magnetic behavior comparable to that obtained in the longtime heat treated industrial GO steels. Thus, the proposed approach allows reach the equal material's quality at significantly shortened manufacturing time and lower energy consumption as compared to the conventional process of GO steel fabrication.

In the present work, we have used an adjusted temper rolling process for development of particular textures {100}

Samples of FeCoNbBCu alloy were nanocrystallized under zero field annealing (ZF) and transverse field annealing (TF) conditions. A reduction in coercivity for TF samples with respect to ZF sample (16 and 45 A/m, respectively) is observed. Kerr microscopy images show a well-defined parallel domain structure, transversally oriented to the ribbon axis for the TF sample unlike for the ZF sample, for which a complex pattern is observed with large and small domains at the surface of the ribbon. Although Mössbauer spectra are clearly different for the two studied samples, Mössbauer studies confirm that there is no significant difference between the hyperfine field distributions of TF and ZF samples but only the relative intensity of the 2nd and 3rd lines A (related to the angle between the gamma radiation and the magnetic moments, α). However, for TF annealed samples α = 90 deg (A = 4), indicating that the magnetic moments lay on the plane of the ribbon in agreement with the well-defined domain structure observed by Kerr microscopy, ZF annealed samples show A = 1.8. This value is close to that of a random orientation (A = 2) but smaller, indicating a slight preference for out of plane orientations. Moreover, it is clearly smaller than that of the as-cast amorphous samples A = 2.8, with a preference to in-plane orientations. The application of the law of approach to saturation yields a larger effect of the inhomogeneities in ZF sample with respect to TF one., This work was supported by the Spanish Ministry of Science and Innovation and EU FEDER (Project MAT2013-45165-P), the PAI of the Regional Government of Andalucía, and the Slovak Projects APVV-0492-11, VEGA 2/0192/13. The Slovak team acknowledges also the support of the Operational Program “Research and Development” financed through European Regional Development Fund through the Projects ITMS 26220120019 and ITMS 26220220061.

The influence of both longitudinal and transverse magnetic field applied during heat treatment on the soft magnetic behavior in the amorphous and nanocrystalline Fe38Co38Mo8B15Cu alloys has been investigated. Sheared loops with good field linearity were achieved after annealing in transverse magnetic field. The value of induced anisotropy constant Ku after such annealing increased from 440 J/m3 for thermally relaxed amorphous samples up to 935 J/m3 for alloys in advanced stage of primary crystallization. The nanocrystallization under a presence of the longitudinal magnetic field results in squared hysteresis loops that are characterized by reduction of coercivity Hc to 3–7 A/m. Such low Hc values surpass those previously reported for FeCo-based nanocrystalline alloys.

The mechanochemical synthesis of Cu/FeS, Pb/FeS and Sb/FeS nanoparticles was investigated with the regard to solid-state kinetics. Experiments were performed in a planetary mill and in an eccentric vibratory mill by a high-energy milling of Cu 2 S, PbS and Sb 2 S 3 , respectively with elemental iron under protective atmosphere. Cu, Pb and Sb nanometals were obtained due to the reducing power of iron. The reduction processes are very straightforward and fast and can be carried out at ambient temperature. Nanometals are embedded into FeS matrix forming metal/ceramics nanocomposites. XRD, SEM and magnetometry methods were used to characterize the ball-milled products. Solid-state kinetics has been evaluated based on magnetometry data.

Classical transformations from rapidly quenched amorphous into (nano)crystalline state monitored by time and temperature evolution of electrical resistivity are discussed as a typical case. Common and different features observed in these transformations, related to local structural and chemical arrangements, are compared with special cases, e.g. sharp increase of resistivity during energy-intensive crystallization observed in Fe–Ni based amorphous systems. A drastic increase of electrical resistivity during transformation in Al–V system is attributed to the formation of nanoquasicrystalline structures with a predicted pseudogap in the electron density at the Fermi level. The results are correlated with microstructure observations and with data from routinely used methods of kinetic analysis with respect to the expected local atomic ordering in amorphous precursor systems.