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NiCr2O4 nanoparticles with average particle size ∼15 nm, a single-domain size maintains the bulk canted antiferromagnetic ground state, were synthesized by a microwave combustion method. The magnetic behavior was carefully investigated by static and dynamic magnetic susceptibility measurements. In addition to a spin-glass-like behavior below paramagnetic-ferrimagnetic transition at T C, the NiCr2O4 nanoparticles demonstrate a low-temperature cluster spin glass transition below the spin canting transition T S, which manifests itself as a magnetic anomaly peak around ∼12 K (at 100 Oe) in the zero-field cooled magnetization with a relatively stronger field dependence in a 'de Almeida-Thouless' line for spin glasses. The AC susceptibility analyses in different approaches demonstrate a larger relative peak temperature variation per frequency decade and a longer characteristic relaxation time in the order of 0.04 and 10−7 s, against 0.01 and 10−9 s for the high-temperature blocking, indicating the slow spin dynamics for the low-temperature cluster glassy phase. A field-temperature magnetic phase diagram is proposed for the single-domain NiCr2O4 nanoparticles. [ABSTRACT FROM AUTHOR]

CoMn2O4, known for its extensive range of applications, has been subject to limited investigations regarding its structure dependent magnetic properties. Here, we have examined the structure dependent magnetic properties of CoMn2O4 nanoparticles synthesized through a facile coprecipitation technique and are characterized using x-ray diffractometer, x-ray photoelectron spectroscopy (XPS), RAMAN spectroscopy, transmission electron microscopy and magnetic measurements. Rietveld refinement of the x-ray diffraction pattern reveals the coexistence of 91.84% of tetragonal and 8.16% of cubic phase. The cation distribution for tetragonal and cubic phases are (Co0.94Mn0.06)[Co0.06Mn1.94]O4 and (Co0.04Mn0.96)[Co0.96Mn1.04]O4, respectively. While Raman spectra and selected area electron diffraction pattern confirm the spinel structure, both +2 and +3 oxidation states for Co and Mn confirmed by XPS further corroborate the cation distribution. Magnetic measurement shows two magnetic transitions, Tc1 at 165 K and Tc2 at 93 K corresponding to paramagnetic to a lower magnetically ordered ferrimagnetic state followed by a higher magnetically ordered ferrimagnetic state, respectively. While Tc1 is attributed to the cubic phase having inverse spinel structure, Tc2 corresponds to the tetragonal phase with normal spinel. In contrast to general temperature dependent H C observed in ferrimagnetic material, an unusual temperature dependent H C with high spontaneous exchange bias of 2.971 kOe and conventional exchange bias of 3.316 kOe at 50 K are observed. Interestingly, a high vertical magnetization shift (VMS) of 2.5 emu g−1 is observed at 5 K, attributed to the Yafet–Kittel spin structure of Mn3+ in the octahedral site. Such unusual results are discussed on the basis of competition between the non-collinear triangular spin canting configuration of Mn3+ cations of octahedral sites and collinear spins of tetrahedral site. The observed VMS has the potential to revolutionize the future of ultrahigh density magnetic recording technology. [ABSTRACT FROM AUTHOR]

Anisotropic magnetoresistance (AMR) and related planar Hall resistance (PHR) are ubiquitous phenomena of magnetic materials. Although the universal angular dependences of AMR and PHR in magnetic polycrystalline materials with one order parameter are well known, no similar universal relation for other class of magnetic materials are known to date. Here a general theory of galvanomagnetic effects in magnetic materials is presented with two vector order parameters, such as magnetic single crystals with a dominated crystalline axis or polycrystalline non-collinear ferrimagnetic materials. It is shown that AMR and PHR have a universal angular dependence. In general, both longitudinal and transverse resistivity are non-reciprocal in the absence of inversion symmetry: Resistivity takes different values when the current is reversed. Different from simple magnetic polycrystalline materials where AMR and PHR have the same magnitude, and π /4 out of phase, the magnitudes of AMR and PHR of materials with two vector order parameters are not the same in general, and the phase difference is not π /4. Instead of π periodicity of the usual AMR and PHR, the periodicities of materials with two order parameters are 2 π. [ABSTRACT FROM AUTHOR]

Polycrystalline GdFe1âˆ' x Ni x O3 (x  = 0.00, 0.02, 0.04) samples was synthesised using a glycine assisted solâ€"gel method to investigate the enhanced magnetic and electric properties of Ni substituted GdFeO3 systems. TG-DSC analysis of prepared samples confirms that GdFe1âˆ' x Ni x O3 have good thermal stability in high temperatures. The system has been stabilized in an orthorhombic structure with space group Pbnm. The elemental composition of GdFe1âˆ' x Ni x O3 has been estimated from EDAX spectrum. The results showed oxygen deficiency on increasing the Ni substitution and it has been supported by Rietveld refinement. FE-SEM images and Brunauerâ€"Emmettâ€"Teller analysis reveals that GdFe1âˆ' x Ni x O3 is a highly porous material and its porosity and specific area increases with Ni substitution. Magnetic measurements indicates that the system exhibited ferrimagnetic behaviour at low temperatures and canted antiferromagnetic behaviour at room temperature. For x  = 0.04 Ni content, magnetization reversal for applied field of 25 Oe has been observed. Increased coercivity of GdFeO3 with Ni substitution has been attributed to the grain size effect. From electrical point of view, dielectric permittivity of GdFeO3 has been enhanced with Ni substitution. This enhancement has been attributed to the cumulative effects of hopping of Fe2+â€"Fe3+ ions, grainâ€"grain boundary contribution, and space charge polarization. The role of grainâ€"grain boundary contribution is evident from electric modulus spectrum. The space charge effect has been realized in both impedance spectrum and dielectric loss. Temperature-dependent dielectric studies were conducted to understand the mechanisms and various aspects that contribute to the dielectric enhancement. A highly lossy capacitive nature in the P â€" E loop also suggests space charge effects due to Ni substitution in Fe sites. Availability of free charge carrier concentration is correlated with the optical properties of GdFe1âˆ' x Ni x O3. The decrease of optical band gap (2.5â€"2.21 eV) on increasing Ni content suggests the increasing electronic contribution in the system. [ABSTRACT FROM AUTHOR]

Mn4N is a typical transition metal nitride with antiperovskite structure. Mn4N films and Mn4N based heterostructures have attracted much attention for potential applications due to their ferrimagnetism, high thermal stability, perpendicular magnetic anisotropy and low saturation magnetization. The fascinating physical properties promise a series of novel applications in next-generation electronic, memory and energy-efficient devices. In this review, the progress of Mn4N films and its heterostructures are systematically summarized and discussed. In the 1st part, the various Mnâ€"N compounds with different phases are introduced, and the basic properties of manganese nitrides are emphasized in details, especially for the properties, superiorities and applications in spintronics of Mn4N. The 2nd part summarizes the fabrication methods, structure and physical properties of Mn4N films. Besides, the underlying mechanisms of Mn4N films and other similar materials are briefly reviewed. In the 3rd part, the tunable magnetic properties of Mn4N films are discussed, including the manipulations methods of different Mn4N heterostructures in recent years. The 4th part highlights the physical properties of Mn4N films doped with other metals, including Co, Ni, and other heavy metal elements. The 5th part illustrates the potential applications of Mn4N films based on the physical properties discussed before. Finally, challenges and future prospects for Mn4N films are discussed, which could provide guidance for developing novel applications and designing functional devices. [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]

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]

All-optical magnetic switching in ferromagnetic thin films reveals an unprecedented route to manipulate magnetic configurations for future ultrafast and energy-efficient magnetic storage. In this study, the relationship between the all-optical magnetic switching and interlayer exchange coupling was investigated in a [Co/Pt]n/Ru/GdFeCo synthetic ferrimagnetic heterostructure. While a thermal demagnetization is dominant in a single GdFeCo alloy film after laser sweep, the magneto-optical interaction transits to a clear all-optical magnetic switching after GdFeCo film being exchange coupled with a [Co/Pt]n multilayer. Meanwhile, the established interlayer exchange coupling can also significantly increase the optical-induced magnetization switching ratio in [Co/Pt]n multilayer after single-pulse laser illumination. A threshold interlayer exchange coupling strength of ∼0.31 erg cm−2 was confirmed for achieving a deterministic (∼90%) optical-induced magnetization switching ratio after multi-pulse laser illumination. This study demonstrates a clear correlation between interlayer exchange coupling and all-optical magnetic switching, offering a promising engineering pathway for high density all-optical magnetic recording. [ABSTRACT FROM AUTHOR]

The double perovskite La2FeMnO6 is ideally expected to be a ferrimagnet with a low saturation moment of 1 μB/f.u. Inhomogeneity in the Fe/Mn sites, along with other lattice disorders, can modify the exchange interactions in the material and result in a net saturation moment of more than 1 μB/f.u. Here, the origin of complicated magnetic behavior is examined of a pure phase La2FeMnO6 sample prepared by the sol-gel method. XRD analysis established that the material crystallizes in the orthorhombic Pbnm symmetry. The comprehensive analysis of x-ray photoelectron spectroscopy, x-ray near edge structure, and magnetic measurements acknowledge an antiferromagnetic coupling between Fe3+ and Mn3+ cations, thereby, resulting in the ferrimagnetic ground state for La2FeMnO6. The magnetic hysteresis loop obtained at 5 K shows a large coercivity of ∼820 Oe and a saturation moment of 1.6 μB/f.u., hinting at partial B-site ordering in La2FeMnO6. The ac susceptibility and dc magnetization measurements indicate the existence of magnetic glassy states (of cluster-glass type) with two distinct dynamical freezing points at ∼27 and 92 K, along with a Griffiths-like phase in the material. The experimental results are discussed taking several possible exchange interactions among Fe3+ and Mn3+ ions in the system into consideration. The magnetic complexity of this system makes it attractive for fundamental research and technological applications. [ABSTRACT FROM AUTHOR]

We investigated a polycrystalline sample of the ferrimagnetic compound Tb0.15Co0.85 by magnetometry and small-angle neutron scattering (SANS). The magnetization curve at 300 K is characteristic for soft ferrimagnets but at 5 K the hysteresis indicates the existence of magnetic domains. The magnetic SANS signal suggests that at 300 K the Tb and Co moments are correlated over large volumes within the micrometer-sized grains with correlation lengths >100 nm. At 5 K, however, the magnetic SANS analysis reveals a reduced correlation length of around 4.5 nm, which indicates the formation of narrow magnetic domains within the ferrimagnet with one dimension being in the nm range. We attribute the observed changes of the domain structure to the temperature-dependence of the magnetic properties of the Tb sublattice. [ABSTRACT FROM AUTHOR]

We investigated a polycrystalline sample of the ferrimagnetic compound Tb0.15Co0.85 by magnetometry and small-angle neutron scattering (SANS). The magnetization curve at 300 K is characteristic for soft ferrimagnets but at 5 K the hysteresis indicates the existence of magnetic domains. The magnetic SANS signal suggests that at 300 K the Tb and Co moments are correlated over large volumes within the micrometer-sized grains with correlation lengths >100 nm. At 5 K, however, the magnetic SANS analysis reveals a reduced correlation length of around 4.5 nm, which indicates the formation of narrow magnetic domains within the ferrimagnet with one dimension being in the nm range. We attribute the observed changes of the domain structure to the temperature-dependence of the magnetic properties of the Tb sublattice. [ABSTRACT FROM AUTHOR]

This article reports exchange bias (EB) in nanocrystalline cobalt chromite CoCr2O4, - a phenomenon manifested by loop shift followed by increase in coercivity after cooling the sample in static magnetic field. The average particle size of the nanocrystalline CoCr2O4 is 30 nm, confirmed from transmission electron microscopy images. Thermal variation of magnetization data M(T), in zero field cooling (ZFC) and field cooling (FC) modes depict long range order below the lock-in transition at TL≈16 K, spin-spiral transition at TS≈28 K and a collinear ferrimagnetic state at TC≈100 K. Magnetic hysteresis loops are recorded in ZFC and FC modes at different cooling fields (). In addition, hysteresis loops are recorded in FC mode for a wide temperature range. In both cases, a clear signature of conventional exchange bias effect is observed. Analysis of the training effect in magnetic hysteresis loop and temperature dependent ac susceptibility (χac) at different frequencies suggest that the surface spins of CoCr2O4 nanoparticles play an important role in controlling the magnetic properties, and enhance the EB effect in collaboration with competition between non-collinear spiral spin state and collinear long range ferrimagnetic order. [ABSTRACT FROM AUTHOR]

This article reports exchange bias (EB) in nanocrystalline cobalt chromite CoCr2O4, - a phenomenon manifested by loop shift followed by increase in coercivity after cooling the sample in static magnetic field. The average particle size of the nanocrystalline CoCr2O4 is 30 nm, confirmed from transmission electron microscopy images. Thermal variation of magnetization data M(T), in zero field cooling (ZFC) and field cooling (FC) modes depict long range order below the lock-in transition at TL≈16 K, spin-spiral transition at TS≈28 K and a collinear ferrimagnetic state at TC≈100 K. Magnetic hysteresis loops are recorded in ZFC and FC modes at different cooling fields (). In addition, hysteresis loops are recorded in FC mode for a wide temperature range. In both cases, a clear signature of conventional exchange bias effect is observed. Analysis of the training effect in magnetic hysteresis loop and temperature dependent ac susceptibility (χac) at different frequencies suggest that the surface spins of CoCr2O4 nanoparticles play an important role in controlling the magnetic properties, and enhance the EB effect in collaboration with competition between non-collinear spiral spin state and collinear long range ferrimagnetic order. [ABSTRACT FROM AUTHOR]

Cubic spinel CoCr2O4 has recently attained attention due to its multiferroic properties. However, the Co site substitution effect on the structural and magnetic properties has rarely been studied in thin film form. In this work, the structural and magnetic properties of Co1–xNixCr2O4 (x= 0, 0.5) epitaxial thin films deposited on MgAl2O4 (100) and MgO (100) substrates to manipulate the nature of strain in the films using pulsed laser deposition (PLD) technique are presented. The epitaxial nature of the films was manifested through x-ray diffraction (XRD), reciprocal space mapping (RSM) and Rutherford backscattering spectrometry (RBS) measurements. Raman measurements revealed a disappearance of characteristic A1g and F2g modes of the CoCr2O4 with increase in the Ni content. Atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM) studies show a modification of the surface morphology upon Ni substitution. Magnetic measurements disclose that the ferrimagnetic Curie temperature (TC) of the CoCr2O4 in thin film grown on MgAl2O4 (100) and MgO (100) substrates were found to be 100.6 ± 0.5 K and 93.8 ± 0.2 K, respectively. With Ni substitution the TC values were found to be enhanced to 104.5 ± 0.4 K for MgAl2O4 (100) and 108.5 ± 0.6 K for MgO (100) substrates. X-ray photoelectron spectroscopy (XPS) suggests Cr3+ oxidation states in the films, while Co ions are present in a mixed Co2+/Co3+ oxidation state. The substitution of Ni at Co site significantly modifies the line shape of the core level as well as the valence band. Ni ions are also found to be in a mixed 2+/3+ oxidation state. O 1s core level display asymmetry related to possible defects like oxygen vacancies in the films. [ABSTRACT FROM AUTHOR]

We use the spin and valley degrees of freedom to design the bipolar and unipolar valley filter effects based on the graphene-based P/N junction. When the modified Haldane model and staggered potential are applied on the region P, while the off-resonant circularly polarized light and staggered ferromagnetic exchange field are applied on the region N, the unipolar valley filter effect emerges with the unidirectional spin–valley current. The direction and type of the unidirectional spin–valley current depend on the phase of the modified Haldane model and the direction of polarized light. Other types of the bipolar valley filter effects are also reported, such as the valley-mixed bipolar spin filter effect, valley-mixed bipolar filter effect, valley-locked bipolar spin filter effect and valley-locked bipolar filter effect. These bipolar filter effects have the similarity that the spin–valley currents flow bidirectionally. These types of the unipolar and bipolar valley filter effects can be also mutually switched by modulating the external fields. Moreover, these unipolar and bipolar valley filter effects are robust against a weak temperature. This work reveals that the graphene-based junction has the potential applications in designing the valley filter device and improving the reprogrammable spin logic. [ABSTRACT FROM AUTHOR]

This paper presents a wireless pressure sensor design based on magnetic fluid displacement over a planar coil and its corresponding inductance change. The design of the pressure sensor is presented followed by its fabrication and characterization. Experimental results show a good correlation with a nonlinear model relating the applied pressure to the change in coil self-resonant frequency. A prototype sensor (radius = 6 mm, thickness = 2 mm) based on the above principal using an oil-based ferrofluid (50 µl, ferrite concentration 2%), a polyimide-embedded planar coil (L = 1 µH), and a 25 µm thick polyimide membrane shows a sensitivity of 3 KHz mmHg−1 with a base-line resonant frequency of f0 = 109 MHz. [ABSTRACT FROM AUTHOR]

The quantum simulation model and the self-consistent computational algorithm we proposed two years ago are utilized to investigate the physical properties of a magnetic nanowire consisting of 3d ions which are coupled antiferromagnetically. In the absence of the external magnetic field, all simulations are started from a spin configuration with all moments in the nanosample randomly oriented and performed from a temperature above the magnetic transition temperature TM down to very low temperature as carried out by previous researchers using the Monte Carlo method, and such obtained results are all physically reasonable, verifying the correctness of the simulation model and computing algorithm. In addition, our calculated results suggest that increasing the surface anisotropy enables an increase in the magnetic transition temperature, although less effectively than by enhancing the Heisenberg exchange strength directly. [ABSTRACT FROM AUTHOR]

We give a brief introduction to the oxide (ZnO, TiO2, In2O3, SnO2, etc.)-based magnetic semiconductors from fundamental material aspects through fascinating magnetic, transport, and optical properties, particularly at room temperature, to promising device applications. The origin of the observed ferromagnetism is also discussed, with a special focus on first-principles investigations of the exchange interactions between transition metal dopants in oxide-based magnetic semiconductors. [ABSTRACT FROM AUTHOR]

A BTO/NZFO ferroelectric/ferromagnetic ceramic composite was prepared by the traditional ceramic method and its permeability was analysed in detail. Results showed that as the BTO fraction increased, the permeability of the composite dropped much more rapidly than that predicted by Kirkpatrick's effective medium model, which was consistent with that usually observed in other ferromagnetic composites. A model was developed to interpret the permeability of ferrite particles with the usual multi-180°-domain structure in the composite by considering both the contributions of spin rotation and domain-wall motion. It was confirmed theoretically that the internal demagnetizing field on the ferrite particles, which was changeable with their shape and dispersion situation, and thus with their fraction, controlled the response of spin rotation and thus the permeability of ferrite particles dispersed in the composite. The rapid decrease in the effective permeability of the composite was ascribed to not only the universal compound effect, formation of defects by ion doping from the coexisting phases and the change in grain size with the ferrite fraction, but also the shielding of the spin rotation response of the ferrite, which depended on its demagnetizing state in the composite. [ABSTRACT FROM AUTHOR]

In this work, we analyse the method of forming magneto-optically active heterostructures based on magnetic layers with different magnetic properties. Layers of one type possess a high effective constant of uniaxial magnetic anisotropy Ku* for which the condition Ku*= Ku - 2pMs² > 0 is fulfilled, where Ku is the constant of uniaxial magnetic anisotropy and 2pMs² is the demagnetizing energy, and layers of the second type used possess in-plane or quasi-in-plane magnetization, in which the condition Ku*= Ku - 2pMs² < 0 holds true. The layers of the first type, which we refer to as layers of positive effective uniaxial magnetic anisotropy, may have the composition Bi2Dy1Fe4Ga1O12 and the layers of second type the composition Bi3Fe5O12, which may have very high magneto-optic (MO) figure of merit and are therefore very attractive for the development of MO transparencies and ultra-fast switches. We discuss the optimization of triple-layer structure parameters aimed at achieving a high MO figure of merit simultaneously with low coercivity and high remanent magnetization and possessing rectangular hysteresis loops. The results of the experimental study of the MO properties achieved in garnet heterostructures fabricated using RF sputtering are also described. We show that the proposed paradigm of using new magnetic material combinations demonstrating significantly improved magnetic and MO properties may be realized when working with heterostructures based on Bi-substituted ferrite garnets grown on (1 1 1)-oriented garnet substrates. [ABSTRACT FROM AUTHOR]

Cadmium telluride (CdTe) and its compounds are the materials of choice for producing industrial quality hard x-ray and gamma ray detectors with high spectral resolution and signal-to-noise ratio. However, optimization of the growth process still proves challenging as the yield is small due to inhomogeneities in the material parameters. Here we investigated the influence of inhomogeneous resistivity on charge collection efficiency of CdZnTe radiation detectors operating at high photon fluxes of incoming radiation. We applied a complex of experimental methods—contactless resistivity and photoconductivity mapping, photoluminescence and laser-induced transient current technique. We observed that the charge collection efficiency at low fluxes is nearly independent of resistivity, while at high fluxes the performance of high resistivity part substantially decreases when compared to the lower resistivity part. This behavior is explained by characteristic evolution of defect structure attaining shallow defect self-compensation during the cooling of the solidified crystal. Instabilities at impurity segregation and temperature gradients at the crystal growth cause different concentration of defects that manifest themselves as deep energy levels within the material bandgap. The defect self-compensation is successfully simulated by theoretical model considering defect reactions in tellurium-saturated CdZnTe. [ABSTRACT FROM AUTHOR]

The electronic structures of Ti2NbSb with Hg2CuTi structure and TiZrNbSb with LiMgPdSn structure are investigated using first-principles calculations. The results indicate that Ti2NbSb is a fully compensated ferrimagnetic spin-gapless semiconductor with an energy gap of 0.13 eV, and TiZrNbSb is a half-metallic fully compensated ferrimagnet with a half-metallic gap of 0.17 eV. For Ti2NbSb, the total energy of the Hg2CuTi structure is 0.62 eV/f.u. higher than that of the L21 structure, which is the ground state, and for TiZrNbSb, the total energy of the structure considered in this work is only 0.15 eV/f.u. larger than that of the ground state. Thus both of them may be good candidates for spintronic applications. [ABSTRACT FROM AUTHOR]

The spin Peltier effect (SPE) in a junction comprising a gadolinium-iron-garnet (GdIG) slab and a Pt film has been investigated around the magnetization compensation temperature of GdIG by means of the lock-in thermography method. When a charge current is applied to the Pt layer, a spin current is generated across the Pt/GdIG interface via the spin Hall effect in Pt. This spin current induces a heat current and a measurable temperature change near the Pt/GdIG interface due to the SPE. The SPE signal in the Pt/GdIG junction shows a sign change around the magnetization compensation temperature, demonstrating the similar temperature dependence of the SPE and the spin Seebeck effect for the Pt/GdIG hybrid system. [ABSTRACT FROM AUTHOR]

Herein, we report the appearance of a large exchange bias effect in a moderate cooling field (cooling field, kOe) for the 314—Sr3YCo4O10.5 material. The exchange bias has started to appear near room temperature and reaches a maximum value of 5.5 kOe at 4 K. The existence of ferrimagnetic clusters in the compensated host in this layered structure originates the large exchange anisotropy. Remarkably, the observed value of moderate magnetic field induced exchange bias field is extremely large in comparison with material systems which are recognized to exhibit giant exchange bias effect. In combination with the feasibility of room temperature application, the appearance of large exchange bias in a moderate cooling field exemplifying the present material system as a promising class of compounds for designing coherent magnetic materials with huge exchange bias in low/moderate magnetic field. [ABSTRACT FROM AUTHOR]

Hysteresis properties and magnetization reversal in TbCo(30 nm) and FeNi(10 nm)/TbCo(30 nm) films with nanoscale antidot lattices are investigated to test the effect of nanoholes on the perpendicular anisotropy in the TbCo layer and the induced exchange bias in the FeNi layer. The antidots are introduced by depositing the films on top of hexagonally ordered porous anodic alumina substrates with pore diameter and interpore distance fixed to 75 nm and 105 nm, respectively. The analysis of combined vibrating sample magnetometry, Kerr microscopy and magnetic force microscopy imaging measurements has allowed us to link macroscopic and local magnetization reversal processes. For magnetically hard TbCo films, we demonstrate the tunability of magnetic anisotropy and coercive field (i.e., it increases from 0.2 T for the continuous film to 0.5 T for the antidot film). For the antidot FeNi/TbCo film, magnetization of FeNi is confirmed to be in plane. Although an exchange bias has been locally detected in the FeNi layer, the integrated hysteresis loop has increased coercivity and zero shift along the field axis due to the significantly decreased magnetic anisotropy of TbCo layer. [ABSTRACT FROM AUTHOR]

Magnetic hysteresis and compensation behavior of a mixed spin-(1, 3/2) Ising model on a square lattice are investigated in the framework of effective field theory based on a probability distribution technique. The effect of random crystal field, ferromagnetic and ferrimagnetic exchange interaction on hysteresis loops and compensation phenomenon are discussed. A number of characteristic phenomena have been reported such as the observation of triple hysteresis loops at low temperatures and for negative values of random crystal field. Critical and double compensation temperatures have been also found. The obtained results are also compared to some previous works. [ABSTRACT FROM AUTHOR]

La2VMnO6is measured to be insulating and ferrimagnetic experimentally. In this study, by substituting V with Nb, La2NbMnO6is investigated using the density functional theory. The calculated results indicate that La2NbMnO6is also ferrimagnetic and exhibits the half metallic properties due to the strong electron correlation of Mn. The valence states of Nb and Mn are assigned to be +4 and +2 in La2NbMnO6, respectively, which are different from V3+/Mn3+in La2VMnO6. [ABSTRACT FROM AUTHOR]

We report on the magnetic and magnetoelectric properties of the Y-type hexaferrite BaSrZnMgFe12O22, which undergoes transitions from a collinear ferrimagnetic phase to a proper screw phase at 310 K and to a longitudinal conical phase at 45 K. Magnetic and electric measurements revealed that the magnetic structure with spiral spin order can be modified by applying a magnetic field, resulting in magnetically controllable electric polarization.It was observed that BaSrZnMgFe12O22 exhibits an anomalous magnetoelectric memory effect: the ferroelectric state can be partially recovered from the paraelectric phase with collinear spin structure by reducing magnetic field at 20 K. We ascribe this memory effect to the pinning of multiferroic domain walls, where spin chirality and structure are preserved even in the nonpolar collinear spin state. [ABSTRACT FROM AUTHOR]

Change in the magnetic entropy and specific heat capacity in Fe3Se4 nanorods synthesized by a wet-chemical method in a broad temperature (215–340 K) and magnetic field range (0–60 k Oe) was studied. The isothermal magnetic entropy change (ΔSM) is estimated by an indirect method from the isothermal magnetization curves measured in this temperature range. of  −46  ×  10−2 J kg−1 · K−1 was obtained at ~317 K when the field was changed from 0 to 60 kOe. The maximum in the isothermal magnetic entropy change (ΔSM) is observed in close proximity to TC (~323 K), which is linked to the order–disorder transition. The nature of this transition was analyzed by universal curve behavior. The temperature and magnetic field dependence of specific heat capacity was studied and analyzed to estimate the adiabatic temperature change (ΔTad). The magnetic entropy change of Fe3Se4 nanoparticles is found to be comparable with similar ferrite and manganite nanoparticle systems and a broad operating temperature window of ~30 K was observed around room temperature. [ABSTRACT FROM AUTHOR]

3d transition metal-based magnetic nanowires (NWs) are currently considered as potential candidates for alternative rare-earth-free alloys as novel permanent magnets. Here, we report on the magnetic hardening of Fe30Co70 nanowires in anodic aluminium oxide templates with diameters of 20 nm and 40 nm (length 6 μm and 7.5 μm, respectively) by means of magnetic pinning at the tips of the NWs. We observe that a 3–4 nm naturally formed ferrimagnetic FeCo oxide layer covering the tip of the FeCo NW increases the coercive field by 20%, indicating that domain wall nucleation starts at the tip of the magnetic NW. Ferromagnetic resonance (FMR) measurements were used to quantify the magnetic uniaxial anisotropy energy of the samples. Micromagnetic simulations support our experimental findings, showing that the increase of the coercive field can be achieved by controlling domain wall nucleation using magnetic materials with antiferromagnetic exchange coupling, i.e. antiferromagnets or ferrimagnets, as a capping layer at the nanowire tips. [ABSTRACT FROM AUTHOR]

Ferroelectric and magnetic properties of Fe1−xMnxV2O4 (0 ≤ x ≤ 0.5) spinels are investigated on the basis of dielectric, polarization, and susceptibility measurements. Ferroelectric polarization is discovered in collinear ferrimagnetic and Yafet–Kittel magnetic phases for 0.1 ≤ x ≤ 0.4, which can be tuned by a magnetic field. As orbital-active Fe2+ is substituted with Mn2+, ferroelectric polarization decreases for 0 ≤ x ≤ 0.4 and disappears for x = 0.5. We propose that the two polar components in ferroelectric polarization originate from the exchange striction mechanism and the spin-current model, respectively. [ABSTRACT FROM AUTHOR]

Structural, electronic, and magnetic properties of a Heusler-type CoFeCrAl alloy have been investigated experimentally and by model calculations, with a focus on the alloy’s spin-gapless semiconductivity. The as-quenched samples are ferrimagnetic at room temperature with a Curie temperature of about 456 K, which increases to 540 K after vacuum annealing at 600 °C for 2 h. The saturation magnetizations of the as-quenched and 600 °C-annealed samples are 1.9 µB/f.u. and 2.1 µB/f.u., respectively, which are very close to the value predicted by the Slater–Pauling curve. The resistivity shows a nearly linear decrease with increasing temperature, from about 930 µΩ cm at 5 K to about 820 µΩ cm at 250 K, with dρ/dT of about  −5   ×   10−7 Ω cm K−1. We explain this high resistivity and its temperature dependence as imperfect spin-gapless semiconducting behavior, with a negative band-gap parameter of 0.2 eV. [ABSTRACT FROM AUTHOR]

We present wavelength-dependent measurements of Kerr rotation and ellipticity for ferrimagnetic Tb30Fe70 thin films in the optical range of 225 nm–726 nm (1.7 eV to 5.5 eV). The thicknesses of the magnetic layers vary from 19 nm to 83 nm. Strong optical interference effects in the magneto-optical spectra are observed for films grown on commonly used SiO2/Si substrates, which may easily be misinterpreted as spectral signatures of Tb. This strong optical interference feature can be fully suppressed by depositing magnetic Tb-Fe films on glass substrates. [ABSTRACT FROM AUTHOR]

Thermal birefringence–induced depolarization in terbium gallium garnet (TGG) ceramic rods has been numerically evaluated for the geometry and heating conditions in a previous experiment. In this model, the spatially resolved heat transfer coefficient corresponding to natural convection cooling and the offset of the beam from the rotational axis of the rod have been incorporated and the realistic beam profile used in the experiment has been considered. A resulting beam depolarization ratio of 4.3 × 10−4 has been calculated for an input power of 117 W. The results were found to be in good agreement with the measured values. Furthermore, a parametric study of the depolarization ratio for higher input powers has been performed leading to a depolarization ratio of 3.3 × 10−2 for 1 kW input power. [ABSTRACT FROM AUTHOR]

A first-principles approach is employed to study the structural, electronic, and magnetic properties of RbCaX2 (X = C, N, and O) full-Heusler compounds. It is observed that RbCaN2 and RbCaO2 are new d0 half-metals with an integer magnetic moment of 3 μB and 1 μB in their ferrimagnetic ground states, respectively, while RbCaC2 is a common metallic compound. Analysis of the density of states of these compounds indicates that the magnetic moment and furthermore, the half-metallicity primarily originate from the spin-polarization of the p-like states of N and O atoms. The half-metallic (HM) gaps of RbCaN2 and RbCaO2 are notably large; thus, the half-metallicity is robust against lattice distortion. Such materials are suitable to be grown on various semiconductor substrates. In addition, for RbCaN2 and RbCaO2, four possible terminations of the surface are also calculated. [ABSTRACT FROM AUTHOR]

Y3Fe5O12 (YIG) films with a periodic-antidot-array structure fabricated by laser micro-processing is shown to exhibit clear characteristics of two-dimensional (2D) magnonic crystals. The experimental results demonstrate that the spin-wave-resonance spectra in the YIG films are modulated by the periodic antidot structure. The frequency and lattice-constant dependences of the spectra are well reproduced by a numerical calculation based on magnonic band structures of the 2D magnonic crystals. Since the laser micro-processing is compatible with various thin-film fabrication methods, it can be a powerful tool for constructing magnonic crystals. [ABSTRACT FROM AUTHOR]

We have grown an ultrathin epitaxial Fe/MgO bilayer on (Ga, Mn)As by e-beam evaporation in UHV. The system structure has been investigated by high resolution transmission electron microscopy (TEM) experiments which show that the Fe and MgO films, covering completely the (Ga, Mn)As, grow with the epitaxial relationship Fe[100](001) ∥ MgO[110](001) ∥ (Ga,Mn)As[110](001). The magnetic reversal process, studied by the magneto-optical Kerr effect (MOKE) at room temperature, demonstrates that the iron is ferromagnetic and possesses a cubic anisotropy, confirming the epitaxy relationship found with TEM. Resistivity measurements across the barrier display a non-Ohmic behavior characterized by cubic conductance as a function of the applied voltage suggesting tunneling-dominated transport across the barrier. [ABSTRACT FROM AUTHOR]

The methodology for adapting a standard micromagnetic code to run on graphics processing units (GPUs) and exploit the potential for parallel calculations of this platform is discussed. GPMagnet, a general purpose finite-difference GPU-based micromagnetic tool, is used as an example. Speed-up factors of two orders of magnitude can be achieved with GPMagnet with respect to a serial code. This allows for running extensive simulations, nearly inaccessible with a standard micromagnetic solver, at reasonable computational times. [ABSTRACT FROM AUTHOR]

Multiferroicity in CoCr2O4 is generally regarded to emerge from the onset of noncollinear spiral magnetic order (Ts ≈ 28 K) due to the inverse Dzyaloshinskii–Moriya interaction, far below the temperature of collinear ferrimagnetic transition (Tc ≈ 96 K). So far, the possibility of multiferroicity appearing in collinear magnetic order has been rarely explored. Here, we report a magnetodielectric effect emerging from the onset of collinear ferrimagnetic transition Tc in CoCr2O4. Based on the postulation of non-centric crystal symmetry and Landau theory, we deduce that such a magnetodielectric effect is attributed to the coexistence of electric and magnetic ordering by the magnetoelectric coupling below Tc. Our results suggest that CoCr2O4 is a natural multiferroic in both noncollinear spiral and collinear magnetic ordering. [ABSTRACT FROM AUTHOR]