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Current-induced magnetization switching in compensated ferrimagnetic materials by the spin–orbit torque (SOT) effect is promising for the next generation information storage devices. In this work, we report the current-induced deterministic field-free magnetization switching of the perpendicular Tb-Co ferrimagnet layer in a Co/Ti/Tb-Co trilayers. We found that the switching proportion and polarity of the Tb-Co ferrimagnet depend on the magnetization direction of the in-plane Co layer. The switching process revealed by magneto-optical Kerr microscope imaging further confirmed the current-induced field-free switching of the Tb-Co layer. We also demonstrated the large SOT effective field and the perpendicular effective field acting on the Tb-Co layer, by utilizing the second harmonic voltage measurement and the current-induced loop shift method. The large interfacial SOT efficiency and deterministic field-free magnetization switching in the trilayers structure may accelerate the application of ferrimagnet in SOT memory devices. [ABSTRACT FROM AUTHOR]

In this study, we have investigated amorphous 20-nm-thick Tb/Fe80Co20 multilayer samples with different individual layer thicknesses and their corresponding alloy counterpart. In particular, the structural and magnetic properties were analyzed upon post-annealing. Up to a certain critical thickness of the individual layers in the multilayer, no significant difference between the multilayers and the alloy is observed in their as-deposited states, which indicates the importance of interfacial intermixing. With a further increase in thicknesses of the individual layers, regions with significant larger Tb content emerge, resulting in a reduced effective Tb moment. The loss in perpendicular magnetic anisotropy upon annealing seems to be delayed for multilayers with thin individual layers compared to the alloy sample. We contribute this behavior to the underlying anisotropic short-range order enforced by the multilayer structure, which hinders the structural relaxation process. At higher temperatures, the multilayers strongly intermix and Fe and Co diffuse through the capping layer. This process leads to a strong enhancement of the saturation magnetization at a certain annealing temperature, due to the formation of separated FeCo and Tb-rich TbFeCo alloy layers, until the sample gets oxidized. [ABSTRACT FROM AUTHOR]

The effect of different annealing temperatures on structural, optical and magnetic properties of ZnFe2O4 nanoparticles prepared using the coprecipitation technique has been investigated. With the increase in annealing temperature, crystallinity and average crystallite size of nanoparticles increased. The average crystallite size was found to be 5.55 nm, 6.62 nm and 32.9 nm for the samples annealed at 300 °C, 500 °C and 700 °C, respectively. The X-ray diffraction and Fourier-transform infrared spectroscopy revealed the formation of a cubic spinel structure. The optical direct and indirect bandgap energy decreased with an increase in annealing temperature. The saturation magnetization increased from 16.38 emu/g to 25.91 emu/g. The M–H curves depicted the magnetic phase transition from superparamagnetic to ferrimagnetic. The electrical properties were investigated using an impedance analyzer in the frequency range of 300 Hz to 1 MHz. The conduction properties showed enhancement with increased annealing. The humidity sensing properties were investigated in the range of 15–90% RH and revealed a strong dependence of adsorption capacity on the annealing temperature. Electrical conductivity improved with increased humidity. Excellent humidity sensitivity was observed for ferrites annealed at 700 °C attributed to increased crystallinity and reduced lattice strain making them a potential candidate for use in humidity sensors. [ABSTRACT FROM AUTHOR]

The dynamic response of magnetically ordered materials to an ultrashort external stimulus depends on microscopic parameters, such as magnetic moment, exchange, and spin–orbit interactions. Whereas it is well established that, in multicomponent magnetic alloys and compounds, the speed of demagnetization and spin switching processes has an element‐specific character, the magnetization damping was assumed to be a universal parameter for all constituent magnetic elements irrespective of their different spin–orbit couplings and electronic structure. Herein, experimental and theoretical evidence for an element‐specific magnetic damping parameter is provided by investigating the ultrafast magnetization response of a high‐anisotropy ferrimagnetic DyCo5 alloy to femtosecond laser excitation. Strikingly different demagnetization and remagnetization dynamics of Dy and Co magnetic moments is revealed by employing femtosecond laser pump–X‐ray magnetic circular dichroism probe measurements combined with atomistic spin dynamics (ASD) simulations using ab initio calculated parameters. These observations, fully corroborated by the ASD simulations, are linked to the element‐specific spin–orbit coupling strengths of Dy and Co, which are incorporated in the phenomenological magnetization damping parameters. These findings can be used as a recipe for tuning the speed and magnitude of laser‐driven magnetic processes and consequently allow control over various dynamic functionalities in multicomponent magnetic materials. [ABSTRACT FROM AUTHOR]

In situ high-temperature XRD and magnetic field heat treatment (MFHT) under a magnetic field of 50 kOe have been used to investigate the structural and magnetic properties of the D022 Mn3−xGa (x = 0, 0.2, and 0.4). It was found that Mn3−xGa compounds maintain ferrimagnetic D022 phase in the temperature range of 300–700 K, and their magnetic properties were remarkably improved through MFHT. The saturation magnetization (Ms) of Mn3.0Ga at 300 K increased by 37% from 18.3 to 25.0 emu/g after MFHT. All Mn3-xGa samples showed superior thermal stability in magnetization from 300 to 500 K, and they still retained excellent magnetic properties at a temperature of up to 700 K. The magnetization of Mn3.0Ga and Mn2.8Ga showed a positive temperature coefficient from 300 to 400 K. Even at 700 K, Ms and Hc of 24.3 emu/g and 4.5 kOe were retained in Mn2.8Ga, which is excellent for high-temperature applications. In addition, the coercivity mechanism of Mn3−xGa at 700 K was illustrated by minor hysteresis loops measurement, and it was found that the coercivity mechanism of Mn3−xGa at 700 K was dominated by the pinning mechanism. [ABSTRACT FROM AUTHOR]

Pedogenic magnetic fraction in soils is attributed to fine-grained particles, i.e. superparamagnetic grains. In the case of a strongly magnetic geogenic fraction, pedogenic magnetic contribution is hard to detect. To the best of our knowledge, detailed research into the masking of pedogenic superparamagnetic grains and quantification of this effect has not yet been carried out. The principal aim of our research is to quantify the influence of coarse-grained ferrimagnetic fraction on the detection of the superparamagnetic grains. In order to describe the masking phenomenon, volume and frequency-dependent magnetic susceptibility were determined on a set of laboratory prepared samples composed of natural substances: a diamagnetic quartz matrix, detrital coarse-grained ferrimagnetic crystals from alkaline and ultra-alkaline igneous rocks, and superparamagnetic soil concretions formed in the Haplic Cambisol. Mineralogy, concentration, type and grain size of the tested material were described by parameters of environmental magnetism. The magnetic parameters distinguish both geogenic multidomain and pedogenic superparamagnetic grains. The magnetic signal of the superparamagnetic grains is gradually masked by the increasing proportion of multidomain grains of magnetite/maghemite. The experiment clearly describes the masking effect and brings new insight to studies dealing with strongly magnetic soils of natural and/or highly contaminated origin as a tool for estimation of superparamagnetic pedogenic contribution. [ABSTRACT FROM AUTHOR]

Compensated ferrimagnetic materials such as Co–Tb and Co–Gd have been confirmed to have significant spin–orbit torque (SOT) efficiency. However, the large coercivity and a relatively small spin-mixing conductance may hinder the applications of the near compensated ferrimagnets. In this work, we investigate the SOT effect and its potential applications in Ta/Co–Tb/Pt heterostructures. Based on a Co-rich ferrimagnetic alloy, we obtain a significant SOT switching efficiency of 15 ± 1 (10−6 Oe cm2/A) and a considerable effective spin Hall angle of θ eff = 0.270 ± 0.005. Using harmonic Hall measurement, the temperature dependence of the damping-like effective field has been extracted. The SOT efficiency scales linearly with 1/Ms in the high-temperature range but significantly deviates from this linear scaling law at a lower temperature, which is near the compensation point. In the Tb rich Ta/Co–Tb/Pt SOT device, we demonstrate the functionality of a neuron and the dependence of firing possibility on the intensity of coming stimulus, which is mimicked by the SOT switching dynamics in the ferrimagnetic Co–Tb alloy. [ABSTRACT FROM AUTHOR]

Fine Co(OH)2 powder was prepared by simple precipitation from aqueous solutions of cobalt sulfate and sodium hydroxide without using sophisticated reagents and/or approaches. The fine powder was homogeneously mixed with protonated betaine bis((trifluoromethyl)sulfonyl)amide ionic liquid ([Hbet][TFSA] IL), an amide-type hydrophobic protic IL, and then dispersed in ethanol with graphene nanopowder for being spin-coated upon screen-printed carbon electrode (SPCE) to prepare the glucose-reactive electrode. Activation of the electrode was essential to expose the glucose-oxidation activity, and the experimental evidences indicated that Co3O4 converted from Co(OH)2 during the activation process was the active species in charge of glucose oxidation. The electrode showed a wide linear dynamic range for glucose from 1 to 1757 µM with a high sensitivity of 632 µA cm− 2 mM− 1 and a detection limit of 1 µM in the electrolyte containing 0.5 M NaOH and 0.1 M NaCl. The electrode showed no response to common interferants, including alcohols, in the concentration the same as to glucose. However, ascorbic acid in the same concentration level showed severe interference but negligible in the physiological level. This study shows that Co(OH)2 prepared by facile precipitation is qualified of being an efficient electrocatalyst precursor for glucose oxidation, and IL is a good binder for immobilizing the electrocatalyst. [ABSTRACT FROM AUTHOR]

An advanced digital feedback algorithm providing defined waveform shapes of magnetic flux density (as well as induced voltage) is demonstrated. The algorithm is based on the iterative process predicting the exciting field waveform to be used in order to achieve the desired waveform of the voltage induced in the secondary winding along with the use of advanced hardware configuration utilizing appropriate exciting power amplifier (AMP) acting as a voltage-to-current converter. An approach based on the inverse function computation [inverse function digital feedback (IFDF)] applied to the response of the sample under test (SUT) to the initial exciting field waveform was used to estimate the exciting field that should be applied to magnetize the sample. SUT is usually made of ferromagnetic/ferrimagnetic material, thus constituting basically a nonlinear hysteretic system. Due to the nonlinearity and hysteresis, the iterations have to be repeated more times until the differences between actual and ideal waveforms fit into the required limits based on the chosen criteria, such as form factor (FF), total harmonic distortion (THD), and sample Pearson’s correlation coefficient (rxy). The effectiveness of the algorithm is subjected to testing on various magnetic materials in a wide range of frequencies and amplitudes of the exciting field/flux density in order to judge its robustness and stability as well as the number of iterations steps (or time) needed to obtain the satisfactory waveform shape. [ABSTRACT FROM AUTHOR]

Sr-hexaferrite samples were produced via the conventional ceramic method. X-ray diffractometry (XRD) patterns confirmed the single nanocrystal phase as Sr-hexaferrite (SHF) where any pattern peaks of unreacted Fe2O3 phase were not detected. The mean crystallite size values were determined to be 44 ± 3 nm and 41 ± 3 nm for SHF-O1 and SHF-O2, respectively. The chemical bonding peaks of our sample indicated that the structure of Sr-hexaferrite formation was confirmed by FTIR spectra result. Scanning electron microscopy (SEM) images indicated clearly observed porosity regions with relative densities as high as 94 % and 87 % for SHF-O1 and SHF-O2 samples. The vibrating sample magnetometry (VSM) of each sample at 2K and under a magnetic field of 10 kOe yielded saturation magnetizations, Ms of 93.5 and 94.1 emu/g; remanence values, Mr of 76.4 and 67.8 emu/g for SHF-O1 and SHF-O2, respectively. The magnetization loops of both samples indicated a soft ferrimagnetic behaviour in which the saturation magnetizations were higher than those measured at room temperature in the previous studies. The coercivities, Hc were measured to be 150Oe for both samples. The squareness values, SQR (Mr/Ms) were measured to be high, approximately 0.82 and 0.72 for SHFO1 and SHF-O2, respectively. Depending on the adequate values of magnetization an coercivity along with small mean crystallite size and low porosity values of the obtained Sr-hexaferrite samples, we estimate that these samples are likely to be evaluated further for the potential use as thermoseeds in the field of clinical hyperthermia. [ABSTRACT FROM AUTHOR]

Nanocomposites (NCs) comprising (1-x) BiFeO3 (BFO) and x SrFe12O19 (SRF) (x=0.1, 0.2, 0.3, and 0.4) have been prepared by a sol-gel route. Presence of pure phases of both BiFeO3 (BFO) and SrFe12O19 (SRF) in the NCs for x=0.3 and 0.4 has been confirmed by Rietveld analysis of XRD data though a minor impurity phase is observed in the case of x=0.1 and 0.2 NCs. Transmission electron micrographs of the NCs show that particles are mostly spherical with average size of 30 nm. M-H measurements at 300 and 10K indicate predominantly ferrimagnetic behavior of all the NCs with an increasing trend of saturation magnetization values with increasing content of SRF. Dielectric constant (εr) of the NCs at room temperature shows a dispersive behavior with frequency and attains a constant value at higher frequency. εr - T measurements reveal an increasing trend of dielectric constant of the NCs with increasing temperature and show an anomaly around the antiferromagnetic transition temperature of BFO, which indicates magnetoelectric coupling in the NCs. The variation of capacitance in the presence of magnetic field confirms the enhancement of magnetoelectric effect in the NCs. 57Fe Mössbauer spectroscopy results indicate the presence of only Fe3+ ions in usual crystallographic sites of BFO and SRF. [ABSTRACT FROM AUTHOR]

We report the co-existence of longitudinal ferrimagnetic behavior with Néel temperature TN~46.1 K and reentrant transverse spin-glass state at 44.05 K in Tin (Sn) doped cobalt-orthotitanate (Co2TiO4). The ferrimagnetic ordering is resulting from different magnetic moments of Co2+ on the A-sites (3.87 µB) and B-sites (5.069 µB). The magnetic compensation temperature (TCOMP) shifts from 31.74 K to 27.1 K when 40 at. % of "Sn4+" substitutes "Ti4+" at B-sites where the bulk-magnetization of two-sublattices balance each other. For T > TN, the dc-magnetic susceptibility (χdc = M/Hdc) fits well with the Néel's expression for the two-sublattice model with anti-ferromagnetic molecular field constants NBB~15.44, NAB~32.01, and NAA~20.88. The frequency dependence of ac-magnetic susceptibility χac data follows the Vogel-Fulcher law, and the power-law of critical slowing-down with "zν" = 6.01 suggests the existence of spin-clusters (where "z" and "ν" being dynamic critical-exponent and correlation length of critical-exponent, respectively). This system exhibits unusual hysteresis loops with large bipolar exchange-bias effect (HEB~13.6 kOe at 7 K) after zero-field cooling process from an un-magnetized state, and a dramatic collapse of remanence (MR) and coercive field (HC) across TCOMP. The possible origins of such anomalous characteristics were discussed. [ABSTRACT FROM AUTHOR]

We report the co-existence of longitudinal ferrimagnetic behavior with Néel temperature TN ~46.1 K and reentrant transverse spin-glass state at 44.05K in Tin (Sn) doped cobalt-orthotitanate (Co2TiO4). The ferrimagnetic ordering is resulting from different magnetic moments of Co2+ on the A-sites (3.87 µB) and B-sites (5.069 µB). The magnetic compensation temperature (TCOMP) shifts from 31.74 K to 27.1 K when 40 at. % of "Sn4+ " substitutes "Ti4+ " at B-sites where the bulk-magnetization of two-sublattices balance each other. For T > TN, the dc-magnetic susceptibility (χdc = M/Hdc) fits well with the Néel's expression for the two-sublattice model with antiferromagnetic molecular field constants NBB ~15.44, NAB ~32.01, and NAA ~20.88. The frequency dependence of ac-magnetic susceptibility χac data follows the Vogel-Fulcher law, and the power-law of critical slowing-down with "zν" = 6.01 suggests the existence of spin-clusters (where "z" and "ν" being dynamic critical-exponent and correlation length of critical-exponent, respectively). This system exhibits unusual hysteresis loops with large bipolar exchange-bias effect (HEB ~13.6 kOe at 7 K) after zero-field cooling process from an un-magnetized state, and a dramatic collapse of remanence (MR) and coercive field (HC) across TCOMP. The possible origins of such anomalous characteristics were discussed. [ABSTRACT FROM AUTHOR]

We have evaluated the spin-wave stiffness parameter in nanoparticulate powders of Mg1-xZnxFe2O4 ( 0.0≤x≤0.6 ) mixed ferrites from magnetization data obtained at two different ranges of temperature: 5-300?K and 300-750?K . At the lower temperature range the T-dependence of the saturation magnetization, Ms, data could be fitted to the Bloch's law with T3/2. The spin-wave stiffness parameters D were determined from the coefficient of T3/2; being ~132 and ~86?meVÅ for x?=?0.0 and 0.6, respectively, with the corresponding exchange constant JAB of ~1.10 and ~0.72?meV , respectively. The values of D determined from the experimental Curie temperature Tc were ~212 and ~163?meVÅ2 for x?=?0.0 and 0.6, respectively, with the corresponding exchange constant JAB of ~1.77 and ~1.30?meV . The difference in both JAB and D values obtained from the coefficient of T3/2 and from Tc may be attributed to the fact that the magnetic measurements were performed at a different range of temperatures. The results are discussed in terms of the cation distribution among A- and B-sites of occupation on these spinel ferrites. [ABSTRACT FROM AUTHOR]

Dielectric measurements of core-shell BaTiO3-Ni0.5Zn0.5Fe2O4 ferroelectric-ferrimagnetic composites, sintered at two temperatures (1050 °C and 1150 °C), were performed in a broadband frequency range of 10Hz-1 THz at various temperatures of 100-500 K. The comparison of temperature dependences reveals a drastic change of permittivity as a function of sintering temperature, as a result of modifications induced on the microstructural parameters as grain size and density. Effective medium approach was used in order to better describe processes associated with the constituent composite phases. Complex specific resistivity coupled with Maxwell-Wagner-Hashin-Shtrikman model allowed to associate lower frequency processes with grain boundary effects. We concluded that the main factor influencing the electrical properties of core-shell composites is the structure and interfaces, instead of the constituent materials themselves. [ABSTRACT FROM AUTHOR]

For the first time, rare earth doped strontium hexaferrite nanoparticles Sr(1−x)LaxGdySmzFe(12−(z+y))O19 (x = 0.3, y = z = 0.01) were synthesized by the sol–gel combustion method in this paper. A single-phase with space group P63/mmc was confirmed by X-ray diffraction (XRD) and the average crystallite size was found to be 46 nm. The existence of absorption bands of the hexaferrite phase structure was shown by the Fourier transform infrared (FT-IR) spectra. Raman analysis confirms the formation of all crystallographic hexaferrite sites. The effect of the rare earth elements on the nanoparticles' morphology was evaluated by scanning electron microscopy (SEM) analysis. Energy-dispersive X-ray spectroscopy (EDX) results confirm the sample homogeneity. The value of the band gap was found to be 1.52 eV from the UV-vis NIR spectra. The magnetic analysis of the prepared sample revealed at room temperature a coercivity, saturation magnetization, remanence ratio, maximum magnetic energy product, switching field distribution, and a Curie temperature of 4296.39 Oe, 62.29 emu g−1, 0.49, 7.79 KJ m−3, 0.663, and 490 °C, respectively. These results suggest that this material has a significant function in industry, which could be beneficial for recording media applications. Using first-principles calculations, the site preference of the doping elements Sm, Gd, and La, as well as the effect of doping with these elements on the structural, magnetic, and electronic properties of the M-type strontium hexaferrite, was investigated. [ABSTRACT FROM AUTHOR]

Caloric effects of solids can provide us with innovative refrigeration systems more efficient and environment-friendly than the widely-used conventional vapor-compression cooling systems. Exploring novel caloric materials is challenging but critically important in developing future technologies. Here we discovered that the quadruple perovskite structure ferrimagnet BiCu3Cr4O12 shows large multiple caloric effects at the first-order charge transition occurring around 190 K. Large latent heat and the corresponding isothermal entropy change, 28.2 J K−1 kg−1, can be utilized by applying both magnetic fields (a magnetocaloric effect) and pressure (a barocaloric effect). Adiabatic temperature changes reach 3.9 K for the 50 kOe magnetic field and 4.8 K for the 4.9 kbar pressure, and thus highly efficient thermal controls are achieved in multiple ways. [ABSTRACT FROM AUTHOR]

Anisotropy of magnetic susceptibility (AMS) and anisotropy of magnetic remanence (AARM and AIRM) are efficient and versatile techniques to indirectly determine rock fabrics. Yet, deciphering the source of a magnetic fabric remains a crucial and challenging step, notably in the presence of ferrimagnetic phases. Here we use X‐ray micro‐computed tomography to directly compare mineral shape‐preferred orientation and spatial distribution fabrics to AMS, AARM and AIRM fabrics from five hypabyssal trachyandesite samples. Magnetite grains in the trachyandesite are euhedral with a mean aspect ratio of 1.44 (0.24 s.d., long/short axis), and >50% of the magnetite grains occur in clusters, and they are therefore prone to interact magnetically. Amphibole grains are prolate with magnetite in breakdown rims. We identified three components of the petrofabric that influence the AMS of the analyzed samples: The magnetite and the amphibole shape fabrics and the magnetite distribution anisotropy. Depending on their relative strength, orientation and shape, these three components interfere either constructively or destructively to produce the AMS fabric. If the three components are coaxial, the result is a relatively strongly anisotropic AMS fabric (P' = 1.079). If shape fabrics and/or magnetite distribution anisotropy are non‐coaxial, the resulting AMS is weakly anisotropic (P' = 1.012). This study thus reports quantitative petrofabric data that show the effect of magnetite distribution anisotropy on magnetic fabrics in igneous rocks, which has so far only been predicted by experimental and theoretical models. Our results have first‐order implications for the interpretation of petrofabrics using magnetic methods. Key Points: Trachyandesite analyzed with X‐ray microtomography for comparison between magnetic fabrics and the components of the petrofabricMagnetite and amphibole shape fabrics and magnetite distribution constructively or destructively interfere to produce magnetic fabricsDistribution anisotropy significantly affects the anisotropy of magnetic susceptibility and anisotropy of remanent magnetization [ABSTRACT FROM AUTHOR]

Batı and Ertaş [Physica B 513 (2017) 40] presented a study of dynamic magnetic hysteresis loop properties (DMHLFs) of a mixed spin (1/2, 1) Ising system (IS) on a hexagonal lattice within the mean-field theory based on the Glauber dynamics approach. They observed a number of interesting DMHLFs. We extended the investigation of DMHLFs of a mixed spin (1/2, 1) IS on a hexagonal lattice using the path probability method. We also examined the influences of the rate constants on DMHLFs as well as magnetic coercive fields and remanent magnetizations. We observed that some of our results are in quantitatively good agreement with some theoretical works on various ISs and experimental reported works on some magnetic materials as well as works within the melt-spinning method. We also found that the effects of rate constants are more effective on DMHLFs of the magnetization of spin-1 particles than loops of the magnetization of spin-1/2 particles. [ABSTRACT FROM AUTHOR]

Proximity exchange interaction between graphene electrons and nearby magnetic insulators paves the way to create spin-polarised currents for spintronics applications. Different ferro- and ferrimagnetic insulators, such as europium chalcogenides, yttrium iron garnet and cobalt ferrite, have been proposed in the literature to induce magnetic correlations in graphene. We theoretically study electronic transport properties of graphene in close proximity to a strip of a magnetic insulator, when the system is connected to nonmagnetic source and drain leads. To this end, we describe graphene electrons by means of an effective Hamiltonian whose model parameters are extracted from first-principle calculations. We compare the spin-polarization of the electron current calculated for a number of different magnetic insulators, aiming at elucidating the effects of the various model parameters on the efficiency of the device. In particular, we demonstrate that the polarization of the electric current across the device can be tuned by the source–drain voltage. We conclude that the heterostructures based on europium chalcogenides are ideal candidates to achieve high polarisation at low temperature. [ABSTRACT FROM AUTHOR]

We have investigated the structural and magnetic properties of Mn2Ge, using the projector augmented wave (PAW) method within the generalized gradient approximation (GGA). We have observed that the crystal symmetry for Mn2Ge is more likely to be tetragonal like Cu2Sb, rather than the hexagonal symmetry of Ni2In. Different magnetic ordering is assumed for Mn2Ge, based on that the electronic structure calculations are performed for Mn2Ge with antiferromagnetic (AFM), ferrimagnetic (FIM) spin ordering. In the most favorable ground state of Mn2Ge, nearest Mn (I) and Mn (II) are coupled ferromagnetically. The magnetic moments on the Mn(I) and Mn(II) are found to be varying based on their magnetic ordering. When ordering is ferromagnetic between Mn(I) and Mn(II), the magnetic moment on Mn(I) is large and in all other cases Mn(II) has larger magnetic moment. Easy flipping of spins has been observed. [ABSTRACT FROM AUTHOR]

A new ternary compound, Al2Fe3Nd, was prepared via arc melting using a non-consumable tungsten electrode under an argon atmosphere with subsequent annealing at 923 K for 30 days. Its crystal structure was determined using the Rietveld refinement of powder X-ray diffraction data. The results show that Al2Fe3Nd has a hexagonal structure in a space group of P6/mmm (No. 191). It is isostructural with the Al2.5Ni2.5Y compound. It has lattice parameters of a = 8.8625(3) Ǻ and c = 4.1475(2) Ǻ with a calculated density Dcalc = 6.460 g/cm3. The residual factors converge to Rp = 0.0946 and Rwp = 0.1214. In the temperature range of 2–500 K, magnetic susceptibility has been measured. The magnetic susceptibility of Al2Fe3Nd follows the Curie–Weiss law in the temperature range of 410–500 K. The effective magnetic moment μeff and paramagnetic Curie temperature θP were estimated to be 8.59 μB and 399.8 K, respectively. The saturation magnetic moment and magnetic hysteresis loop for the compound were measured under room- and low-temperature conditions. The measurements indicate that the saturation magnetization moment declines with increasing temperature, and the compound is ferrimagnetic in the analytical temperature range of 2–300 K. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this article is to investigate the magnetic properties and the hysteresis loops behavior of a ferrimagnetic cubic nanowire with mixed spins SA = 3/2 and SB = 2. Design/methodology/approach: We have used the Monte Carlo simulation to examine the influences of the exchange interaction JB, the crystal field ∆ and the temperature on the magnetic properties and hysteresis loops of the nanowire. More exactly, we have shown the temperature dependence of the sublattice magnetizations (mA and mB) and the total magnetization (M) for several values of the Hamiltonian parameters, as well as the corresponding phase diagrams. Finally, the effect of an external magnetic field is studied by plotting the hysteresis loops of the system for different values of exchange interaction, crystal field and temperature. Findings: The obtained results show the existence of second-order phase transitions, as well as the compensation behavior. Moreover, according to the values of the Hamiltonian parameters, the system can exhibit one, two or three hysteresis loops. Originality/value: The magnetic nanowires are of great interest in experimental works, but without theoretical explanations, the experimental results cannot be clarified in depth. For this, we contribute through this theoretical study to understand the nanowires, especially those with mixed spins (2, 3/2). [ABSTRACT FROM AUTHOR]

A novel CMOS hexaferrite circulator with a Y-junction structure is designed and fabricated, which is compatible with standard CMOS technology. The spin-coating approach is adopted during the fabrication, in which the photoresist is mixed with nano-hexaferrite powder for preparation of a magnetic thin film in the device. Compared with the traditional circulator with an external permanent magnet for operation, the novel circulator can utilize the spin-coating magnetic film and is compatible with CMOS technology. The remanent magnetization of the adopted hexaferrite thin film can provide the required magnetic field for reciprocity properties. The optimization of impedance matching and the improvements in the related parameters are demonstrated on the novel CMOS circulator. The CMOS circulator exhibits the merits of small volume and easy integration while keeping its promising non-reciprocity properties. The fabrication is conducted based on the standard 180-nm CMOS technology. S-parameter measurements on the circulator show that the device has an isolation of 20 dB over 520 MHz bandwidth at 26.2 GHz. The minimum insertion loss is 1.81 dB. The novel CMOS-compatible circulator has potential application in 5G wireless communication systems. [ABSTRACT FROM AUTHOR]

Using Kaneyoshi approximation in the framework of effective field theory, we have carried out theoretically the magnetic phase transition and hysteresis behavior at a very low temperature in Mn2RhSi Heusler Alloy (Mn2RhSi-HA). The alloy shows to a ferrimagnetic successive phase transition while its atoms exhibit a various successive phase transition with Tt = 0.630 and TC = 1.560. At a very low temperature, we attain that the alloy has a multistep hysteresis behavior having a butterfly-like hysteresis loop with a large coercivity field while the Si1 atom shows a type-II superconducting hysteresis behavior. Step-like hysteresis behavior at low temperature is due to quantum tunneling of the magnetization. So, we suggest Mn2RhSi-HA could be a potential candidate for magnetic storage device application. Moreover, we can conclude that the competition of antiferromagnetic and ferromagnetic exchange couplings leads to the variety of magnetic phase transition and the hysteresis behavior in Mn2RhSi-HA and its atoms. We can also conclude that these atoms and their exchange interactions to other atoms make a significant contribution to controlling the hysteresis behavior of Mn2RhSi-HA, since the Mn and Rh2 core atoms have the same coercivity as that of Mn2RhSi-HA. The obtained results are consistent with the reported experimental and theoretical results of Mn2-based Heusler alloys and other alloys. [ABSTRACT FROM AUTHOR]

Nanocrystalline La1 –xCdxFeO3 (x = 0, 0.05, 0.1, 0.15, 0.2) powders with a narrow homogeneity range (xmax = 0.09 according to X-ray microanalysis and X-ray diffraction data) have been synthesized via coprecipitation followed by thermal annealing at 950°C for 1 h. The addition of Cd2+ cations leads to a decrease in average crystallite size from 10–70 nm at x = 0 to 5–60 nm at x = 0.1 (according to transmission electron microscopy data). The synthesized nanocrystals have ferrimagnetic properties. [ABSTRACT FROM AUTHOR]

The magnetization-induced second-harmonic generation (MSHG) effect was applied to study changes of magnetization distribution caused by H+2 ions implantation in magnetic garnet film of (111) symmetry. The evolution of the magnetization vector m in perpendicular magnetic field H was studied as a function of coherently rotated polarizers by an angle φ. The I2ω(H, φ) intensities exhibit completely different character as compared to the unimplanted film. The experimental results were explained in the frame of a phenomenological model of the MSHG effect, developed for the structure of 3m symmetry, composed of implanted and unimplanted sublayers. The theoretical approach allowed to determine the amplitudes and phases of nonlinear optical susceptibility tensor elements χ[2] as well as the m(H) vector components. In contrast to the linear magneto-optical Faraday effect, application of nonlinear MSHG method allows for simultaneous determination of all components of the magnetization vector in single experiment. It was found that contributions from the sublayers associated with mz components enter to the MSHG effect with opposite signs due to difference in phases of χ[2]. It is shown that m vector in the implanted sublayer undergoes spatial evolution vs H during the magnetization process, with a complex trajectory corresponding to the reorientation of the m(H) from sample plane to the normal direction. The developed methods can be useful in studies of other magnetic materials with intrinsic or artificially introduced inhomogeneities. [ABSTRACT FROM AUTHOR]

By using first-principles calculations, we investigated how to achieve a strong ferromagnetism in Cr-doped Si by controlling the atomic structure and Cr concentration as well as carrier densities. We found that the configuration in which the Cr atom occupies the tetrahedral interstitial site can exist stably and the Cr atom has a large magnetic moment. Using this doping configuration, room-temperature ferromagnetism can be achieved in both n-type and p-type Si by tuning Cr concentration and carrier densities. The results indicate that the carrier density plays a crucial role in realizing strong ferromagnetism in diluted magnetic semiconductors. [ABSTRACT FROM AUTHOR]

Anomalous Hall effect (AHE) has been studied for ferrimagnetic antiperovskite Mn4-xDyxN films grown by molecular-beam epitaxy. The introduction of Dy changes the AHE dramatically, even changes its sign, while the variations in magnetization are negligible. Two sign reversals of the AHE (negative-positive-negative) are ascribed to the variation of charge carriers as a result of Fermi surface reconstruction. We further demonstrate that the AHE current JAH is dissipationless (independent of the scattering rate), by confirming that anomalous Hall conductivity, σAH, is proportional to the carrier density n at 5K. Our study may provide a route to further utilize antiperovskite manganese nitrides in spintronics. [ABSTRACT FROM AUTHOR]

The spin-phonon coupling in magnetic materials is due to the modulation of the exchange integral by lattice vibrations. BaFe12O19 M-type hexaferrite, which is the most used magnetic material as permanent magnet, transforms into ferrimagnet at high temperatures, but no spin-phonon coupling was previously observed at this transition. In this letter, we investigated the temperature-dependent Raman spectra of polycrystalline BaFe12O19 M-type hexaferrite from room temperature up to 780K to probe spin-phonon coupling at the ferrimagnetic transition. An anomaly was observed in the position of the phonon attributed to the Fe(4)O6, Fe(5)O6, and Fe(1)O6 octahedra, evidencing the presence of a spin-phonon coupling in BaM in the ferrimagnetic transition at 720 K. The results also confirmed the spin-phonon coupling is different for each phonon even when they couple with the same spin configuration. [ABSTRACT FROM AUTHOR]

In ferromagnetic/superconducting (FM/SC) planar hybrids, a reentrance of the upper-critical field line Hc2(T) is observed close to Tc. The effect is generally ascribed to the so-called domain-wall superconductivity and has been theoretically explored in great detail. Experimental investigations are limited mostly to FM/SC bilayers in which the FM layers host out-of-plane magnetic domains of strong anisotropy and large width (>300 nm), the SC layer is quite thick (>30 nm), and the external magnetic field was applied normal. To expand our knowledge to until now unexplored conditions, we study a series of Co(dco)/Nb(dNb)/Co(dco) trilayers under a parallel magnetic field; Co outer layers exhibit out-of-plane magnetic domains of weak anisotropy and small width (<150 nm) and the Nb interlayer is very thin (<20 nm). We demonstrate a strong reentrance of Hc2(T) that can be tuned through the irreversible magnetization processes of the FM outer layers, the two-dimensional character of the SC interlayer, and the matching between the interfering SC and FM length scales. These results refine the nature of the reentrance of Hc2(T) in FM/SC hybrids and can motivate new theoretical and experimental investigations. [ABSTRACT FROM AUTHOR]

Critical analysis on the magnetic properties of synthetic ferrimagnet (SyF), Ta/MgO/CoFeB/Ru/ CoFeB/MgO/Ta, is demonstrated via both static and dynamic techniques. With the Ru thickness being 2.3 nm, the coupling between two CoFeB layers becomes orthogonal, which can be used for spin-transfer-torque nano-oscillator (STNO). The fitting of angular dependent ferromagnetic resonance (FMR) allows the precise determination of magnetic anisotropy of each CoFeB layer, the relative magnetizations and the exchange field near the frequency of STNO applications. In addition, the mechanism of resonance broadening at out-of-plane direction is identified to be magnetic inhomogeneity by fitting the angular dependent linewidth of FMR spectra, which provides indispensable information for the future design of STNO devices. [ABSTRACT FROM AUTHOR]

This contribution focuses on the use of modified Rayleigh law as a technique for determining the intrinsic and extrinsic (reversible/irreversible) contributions to the piezoelectric effect up to 150 °C across a broad compositional space, augmenting previous understanding of the BiFeO3-(K0.5Bi0.5)TiO3-PbTiO3 system. At room temperature, a mechanistic explanation of the correlation between crystal symmetry, i.e., tetragonal spontaneous strain, xs, and the Rayleigh relations using Landau theory is provided. The intrinsic response was found to be heavily dependent upon the tetragonal xs, whereby an optimisation between polarization and permittivity was elucidated, leading to enhanced piezoelectric charge coefficients. A c/a ratio of ~1.041 was identified at which the room temperature intrinsic and extrinsic effects were at a maximum; a dinit of 183 x 10-12 m/V and Rayleigh coefficient of 59 x 10-18 m²/V² were measured, resulting in the largest piezoelectric charge coefficients. The piezoelectric charge coefficient d33, intrinsic and extrinsic contributions of these materials were all found to increase up to 150 °C while adhering to the Rayleigh model. The reversible extrinsic component of the total reversible response, dinit, was calculated to be relatively minor, 4.9% at room temperature, increasing to 12.1% at 150 °C, signifying its increasing influence to the piezoelectric effect, as domain wall motion is thermally activated. Hence, the phenomenological interpretation provided here may be used as a roadmap to elucidate the origins of the temperature dependence of the piezoelectric effect. [ABSTRACT FROM AUTHOR]

Flexile single layer electromagnetic wave absorbers were designed by incorporating appropriate amounts of carbon black in a nitrile butadiene rubber matrix along with an optimized amount of magnetic counterpart, namely, barium hexaferrite for applications in S, C, and X-bands. Effective dielectric permittivity and magnetic permeability were measured using cavity perturbation method in the frequency range of 2-12 GHz. The microwave absorbing characteristics of the composites were studied in the S, C, and X-bands employing a model in which an electromagnetic wave is incident normally on a metal terminated single layer. Reflection loss exceeding -20 dB is obtained for all the samples in a wide frequency range of 2-12 GHz when an appropriate absorber thickness between 5 and 9mm is chosen. The impact of carbon black is clearly observed in the optimized composites on the mechanical strength, thickness, band width of absorption, dielectric properties, and absorptivity. [ABSTRACT FROM AUTHOR]

This study investigates the effect of strain on the compensation temperature of ferrimagnetic Tb–Fe films formed on a flexible substrate. The compensation temperature is determined by the anomalous Hall measurement, and an application of 1.2% tensile strain reduces the compensation temperature by 12 K. X-ray magnetic circular dichroism reveals that approximately 5% of Fe magnetic moment and approximately 1% of Tb magnetic moment are reduced by an application of 0.9% tensile strain at the room temperature. To understand the greater reduction in Fe magnetization compared with that in Tb and the compensation temperature reduction simultaneously, a model applying molecular field theory is analyzed. Changes in three types of exchange coupling between Fe and Tb atoms are speculated to be caused by the strain. [ABSTRACT FROM AUTHOR]

The ability to tune and control the magnetic phases of two-dimensional (2D) nanomagnets at room temperature is indispensable for the development of future spintronics and low-dimensional spin circuits. In this work, a first-principles-based investigation combined with a Monte Carlo simulation based on a 2D Ising model is used to investigate the electronic and magnetic behaviour of a recently discovered 2D material, Cr2Ge2Se6 over a large range of strain and electric field strength. This material offers ferromagnetic antiferromagnetic and semiconductor metallic phase transitions in different regimes. In the presence of strain, a colossal enhancement of the critical temperature (Tc) is observed, from 149 K to 885 K. The application of an electric field allows a further enhancement of the Tc to a value of 919 K, offering a supreme enhancement (~517%), compared to its natural condition. The origin of this behavior can be traced to a super-exchange interaction between the Cr and Se atoms and the intrinsic magnetic anisotropy of Cr2Ge2Se6. The presence of external stimuli engenders spontaneous symmetry breaking with an enhanced magnetic moment (~4.36 /Cr atom), a significant intrinsic spin polarisation (~100%) in a half-metallic regime, and a very high critical temperature. The insights of the current investigation could be useful for future developments in multi-stimuli-assisted room-temperature ferromagnetism and electronic phase control, which are of great significance for future magneto-electronic applications. [ABSTRACT FROM AUTHOR]

Compositions of ferrimagnetic NiSmxFe2−xO4 (0.00 ≤ x ≤ 0.25) ceramics were synthesized by the self-propagating sol-gel autocombustion method. Structural information was found using X-ray diffraction. It reveals that all the ceramics possess cubic symmetry of spinel ferrite with a small amount of orthoferrite phase SmFeO3, which is a ferroelectric material. The amount of phases and lattice parameter were determined by the Rietveld refinement method using the Fullprof suite software. As doping concentration increases, the secondary phase fraction of the ferroelectric SmFeO3 also increases. Due to the increase of the ferroelectric phase in NiFe2O4, the electrical properties of doped samples also modify. To know this modification, the electrical properties of these samples have been investigated. The room temperature dielectric and complex impedance analysis have been measured in the frequency range of 1–106 Hz. The dielectric behavior for x = 0.05 concentration (NiSm0.05Fe1.95O4) has a maximum dielectric constant value with a minimal loss tangent. Cole-Cole plot brings out the role of grain and grain boundaries in the bulk. Using impedance study, the resistance and capacitance of grain and grain boundaries have been determined. The ferroelectric behavior has been performed through the P-E (polarization versus electric field) and J-E (leakage current versus electric field) curves at room temperature. [ABSTRACT FROM AUTHOR]

To study the removal of lead (Pb) ions from aqueous solutions, novel magnetite nanoparticles (NPs) of Ni0.31Mg0.15Ag0.04Fe2.5O4 were synthesized by coprecipitation synthesis using metal sulfates, and then coated with Gum Arabic (GA). The prepared NPs were analyzed using various spectroscopic and analytical methods, such as X-Ray diffraction analysis (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray spectroscopy (EDX), Fourier Transform Infra-Red spectroscopy (FT-IR), and Atomic Absorption Spectrophotometer (AAS). By using XRD analysis, the cubic inverse spinel structure of the prepared NPs was proven, showing average values of crystallite size, lattice constant, and density of 28.57nm, 8.32582Å, and 5.2890 g/cm³, respectively. FE-SEM analysis revealed the sphere-like shape of the nanoparticles with a measured crystallite size of 25.93nm. The existence of constituent elements was evidenced by EDX. FT-IR test proved the success of the coating process of magnetite NPs by the presence of the main characteristic absorption bands of GA in the FT-IR spectrum of GA-magnetite NPs. The adsorption of Pb ions by GAmagnetite NPs was shown by AAS analysis, where the concentration of Pb ions decreased from 25ppm to 6.6ppm, reaching 1.1ppm at the time of 25min. The porosity of the NPs and the carboxyl groups in GA played an important role in the process. [ABSTRACT FROM AUTHOR]

Ferrimagnetic greigite (Fe3S4) is widespread in the sedimentary environment. Despite abundant reports of greigite occurrence in marine and lacustrine deposits, its formation mechanisms in deltaic deposits remain poorly studied. Here we investigate greigite in Holocene Yangtze River Delta deposits using granulometric, magnetic, and geochemical methods. The studied cores consist of tidal river, estuary, shallow marine, and delta facies in ascending order. The greigite‐bearing layers are found predominantly in the accreting tidal flat facies during the transgression stage and secondarily in the shallow marine facies during the regression stage of the delta's Holocene development. These sedimentary intervals have a higher total sulfur (TS) content and TS to total organic carbon ratios (TS/TOC) suggesting the accumulation of iron sulfides, including greigite, under reducing estuarine and shallow marine conditions. The greigite‐bearing layers in the tidal flat facies have lower Sr/Ba ratios, in comparison to the shallow marine facies, indicating a lower salinity environment. Supported by the dating results, it is suggested that the higher sedimentation rate of the tidal flat facies, caused by rapid sea‐level rise during the early Holocene, favors the formation and preservation of greigite. Our results indicate that the magnetic detection of greigite provides a simple and useful tool for inferring salinity and sedimentation rate changes, and hence better an understanding of the heterogeneity of depositional processes in Holocene delta environments. Plain Language Summary: Greigite (Fe3S4), an early or late diagenetic magnetic mineral, is an iron sulfide commonly produced during the carbon‐iron‐sulfur (C‐Fe‐S) cycle in aquatic environments. Its occurrence is generally found to be linked to water salinity change, which can be used to infer changes in past environmental conditions such as drought and flood events. So far, studies on greigite have focused on marine and lacustrine deposits. Its formation mechanisms in delta environments remain poorly known, where fresh and marine water mixing results in intensive spatial and temporal salinity change. In this study, environmental magnetic measurement and salinity indictors for example, the ratio of strontium to barium (Sr/Ba), the ratio of total sulfur to total organic carbon (TS/TOC) and TS concentration are combined to reveal greigite occurrence and its formation conditions. Our results show that higher sedimentation rates and marked salinity change associated with rapid sea level rise in the early Holocene is favorable for greigite generation and preservation. We find that magnetic detection of greigite can provide valuable information regarding spatial/temporal variabilities in fresh‐marine water mixing and depositional processes in deltaic environment. Key Points: We identify greigite at the boundary of sedimentary facies with marked salinity change in the Yangtze River DeltaGreigite‐bearing layers occurs predominantly in accreting tidal flat facies with a higher sedimentation rateMagnetic identification of gregite can assist stratigraphic differentiation in delta deposits [ABSTRACT FROM AUTHOR]

We have investigated the anomalous Hall effect (AHE) of a ferrimagnetic GdFeCo film with perpendicular magnetic anisotropy. In the vicinity of magnetization compensation temperature TM, the peak structure or triple loop of the Hall resistance loops is mainly caused by the opposite magnetic moments of the two sublattices of Gd and FeCo, and that can be explained by the mechanism of the two-channel AHE. Furthermore, we demonstrated that the transport properties of the GdFeCo film can be manipulated by ionic liquid gating. When the gate voltage is −4 V, the TM of the GdFeCo film was changed up to 29 K. Our research provides experimental evidence for the design of novel electronic devices. [ABSTRACT FROM AUTHOR]

Rare-earth transition metal (RE-TM) TbFeCo alloy films with adjustable perpendicular switching field and anisotropy are desirable for the applications in high-density spintronic devices. A series of TbFeCo alloy films are fabricated by sputtering a composite target method. The perpendicular magnetic properties of the ferrimagnetic TbFeCo films are investigated by Extraordinary Hall effect (EHE) measurements. With increasing either sputtering power or gas flow rate film composition shifting from FeCo-rich to Tb-rich side is observed and the orientation of magnetic easy axis changing from in-plane, tilted to out-of-plane direction is witnessed. Pronounced change in magnetic properties particularly the coercivity of TbFeCo films is demonstrated, in line with the increased Tb-to-FeCo ratio of the alloy films. It shows TbFeCo films with desirable coercivity can be achieved by proper combination of sputtering power and flow rate. Our work provides an efficient way in tuning the PMA of the sputtered TbFeCo films during the growth and may be used as guidance for designing TbFeCo-based spintronic devices. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of 6Li atomic gas system, with imbalanced spin populations trapped in one-dimension, were systematically investigated using the Static Fluctuation Approximation. The two-body interaction used is an attractive contact potential. The effects of gas parameter 1 (k F a s) and spin polarization p , on the thermodynamic properties and effective magnetic field were investigated. We observed a decrease in μ and an enhancement in h and U with increasing p. At strong interaction and at T = 0. 1 T F , the behavior of entropy with p indicated two different phases. At small spin polarization p < 0. 3 , the system could be in Fulde–Ferrell–Larkin Ovchinnikov (FFLO) state, while above p = 0. 3 , the system might be in normal state. In addition, we found a clear decrease in both μ and U and an enhancement in h with the increase of the interaction strength. Our results are consistent with the reported results obtained by the mean-field Bogoliubov–de Gennes method, the Bardeen–Cooper–Schrieffer (BCS) approximation and Nozieres–Schmitt–Rink (NSR) theory. [ABSTRACT FROM AUTHOR]

Ferrimagnetic materials (FiMs) represent a promising direction for the realization of spin-based devices since they can combine the ultrafast dynamics typical of antiferromagnets in an easier way to control the magnetic state typical of ferromagnets. In this work, we micromagnetically analyze the magnetization dynamics of a current-driving transition metal/rare earth ferrimagnet in a spin Hall geometry as a function of the uncompensation parameter of the angular moments of the two sublattices. We show that, for a uniaxial FiM, a self-oscillation is the only possible dynamical state at the angular momentum compensation point. We also find a finite discontinuity near the magnetization compensation point originated from the demagnetizing field, which controls the type of dynamics behind the switching. We finally show the effect of the interfacial Dzyaloshinskii–Moriya interaction on both the switching time and the self-oscillation frequency and amplitude. [ABSTRACT FROM AUTHOR]

Magnetic stability of iron mineral phases is a key for their use as paleomagnetic information carrier and their applications in nanotechnology, and it critically depends on the size of the particles and their texture. Ferrimagnetic greigite (Fe3S4) in nature and synthesized in the laboratory forms almost exclusively polycrystalline particles. Textural effects of inter-grown, nano-sized crystallites on the macroscopic magnetization remain unresolved because their experimental detection is challenging. Here, we use ferromagnetic resonance (FMR) spectroscopy and static magnetization measurements in concert with micromagnetic simulations to detect and explain textural effects on the magnetic stability in synthetic, polycrystalline greigite flakes. We demonstrate that these effects stem from inter-grown crystallites with mean coherence length (MCL) of about 20 nm in single-domain magnetic state, which generate modifiable coherent magnetization volume (CMV) configurations in the flakes. At room temperature, the instability of the CVM configuration is exhibited by the angular dependence of the FMR spectra in fields of less than 100 mT and its reset by stronger fields. This finding highlights the magnetic manipulation of polycrystalline greigite, which is a novel trait to detect this mineral phase in Earth systems and to assess its fidelity as paleomagnetic information carrier. Additionally, our magneto-spectroscopic approach to analyse instable CMV opens the door for a new more rigorous magnetic assessment and interpretation of polycrystalline nano-materials. [ABSTRACT FROM AUTHOR]

We investigated the effects of surface modification treatment (SMT) on the perpendicular magnetic anisotropy (PMA) and the thermal tolerance of top-pinned magnetic tunnel junctions (MTJs) with a Co/Pt synthetic ferrimagnetic coupling reference layer. Applying an SMT to the bottom Pt layer increased the PMA of the overlying Co/Pt multilayer. X-ray diffraction spectrum analysis revealed that the SMT resulted in a higher crystallinity and smaller lattice spacing in the Co/Pt multilayer in the thinner bottom Pt layer, which may have increased the PMA in the Co/Pt multilayer. The tunnel magnetoresistance (TMR) ratio of the MTJ with SMT increased as the annealing temperature was increased up to 400 °C; conversely, the TMR ratio of the MTJ without SMT decreased at an annealing temperature of 400 °C. Evaluation of the m-H loops revealed that, after annealing at 400 °C, the reference layers in the MTJs after SMT possessed better magnetic properties than those in the MTJs without an SMT; this is attributable to the higher PMA of the reference layers with SMT. EDX line analysis revealed that SMT suppressed Pt diffusion to the MgO barrier, resulting in a higher thermal tolerance and larger PMA of the reference layer. [ABSTRACT FROM AUTHOR]

The antiperovskite Co4N is studied using density functional theory (DFT) calculations and Monte Carlo (MC) simulation within the framework of the Ising model. The structural, density of states (DOS), and band structure calculations show that Co4N is a ferromagnetic material having a higher magnetic moment, a large spin polarization ratio, and exhibits a metallic behavior. The investigated elastic constants, phonon dispersion, and phonon DOS show that the Co4N compound is mechanically and dynamically stable. It is also found that the Co4N is ductile from the Poisson's ratio, Pugh's ratio, and Cauchy pressure. The thermodynamic parameters like heat capacity, Debye and melting temperature are calculated. The magnetization, magnetic susceptibility, and the Curie temperature of magnetic transition are estimated using MC simulations based on the Ising model. The obtained value of TC is in good agreement with available theoretical work. [ABSTRACT FROM AUTHOR]

In this study, antibacterial impact of magnetic nanocomposite (MNC: MoS2/CoFe2O4) and super paramagnetic iron oxide nanoparticle (SPION: Fe3O4-Casein) against staphylococcus aureus was studied. It was expected that such comparative study, address key points in optimization of synthesis and design of nanomaterials, which are supposed to be used as antibacterial agents for magnetic fluid hyperthermia (MFH) purposes. As the results, the MNC and SPION had average sizes of 17±4 nm and 15±5 nm, and diffused homogenously in agarose gel. They both were bacteriostatic against S. aureus at very low concentrations, while were bactericidal at concentrations of 200 µg/mL and more in MFH condition. In conclusion, both MNC and SPION inhibit S. aureus viability when low amplitude (H = 31.16 mT) alternative magnetic field (AMF: f = 150 kHz) was applied. Therefore, both of the nanomaterials are eligible to be considered as antibacterial candidates for treatment of complicated infections in upper respiratory tract or skin. [ABSTRACT FROM AUTHOR]

Ferrimagnetic alloy thin films that exhibit perpendicular (out-of-plane) magnetic anisotropy (PMA) with low saturation magnetization, such as GdCo and Mn4N, were predicted to be favorable for hosting small Néel skyrmions for room temperature applications. Due to the exponential decay of interfacial Dzyaloshinskii–Moriya interaction and the limited range of spin–orbit torques, which can be used to drive skyrmion motion, the thickness of the ferrimagnetic layer has to be small, preferably under 20 nm. While there are examples of sub-20 nm, rare earth-transition metal (RE-TM), ferrimagnetic thin films fabricated by sputter deposition, to date, rare-earth-free sub-20 nm Mn4N films with PMA have only been reported to be achieved by molecular beam epitaxy, which is not suitable for massive production. Here, we report the epitaxial growth of sub-20 nm Mn4N films with PMA at 400 °C–450 °C substrate temperatures on MgO substrates by reactive sputtering. The Mn4N films were achieved by reducing the surface roughness of MgO substrate through a high-temperature vacuum annealing process. The optimal films showed low saturation magnetization (Ms = 43 emu/cc), low magnetic anisotropy energy (0.7 Merg/cc), and a remanent magnetization to saturation magnetization ratio (Mr/Ms) near 1 at room temperature. Preliminary ab initio density functional theory calculations have confirmed the ferrimagnetic ground state of Mn4N grown on MgO. The magnetic properties, along with the high thermal stability of Mn4N thin films in comparison with RE-TM thin films, provide the platform for future studies of practical skyrmion-based spintronic materials. [ABSTRACT FROM AUTHOR]