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Spin–orbit torques (SOTs) provide an efficient way to electrically manipulate the magnetic order in spintronic devices. Compared with conventional ferromagnetic materials, ferrimagnetic materials have the advantages of antiferromagnetically coupled sublattices and induced ultrafast spin dynamics. In this paper, we study the current-induced magnetization switching in the ferrimagnetic Ta/GdFeCo/MgO system. Robust SOT-induced magnetization switching can be achieved at the magnetic compensation temperature point of around 70 K, where the magnetization is nearly zero and the coercivity can reach almost 3 T. The temperature dependence of the SOT efficiency is quantified by the second harmonic method, and the enhanced SOT efficiency near the magnetic compensation temperature is attributed to the negative exchange coupling between the two sublattices of CoFe and Gd. This work demonstrates the SOT switching of the nearly compensated ferrimagnet, with great potential for future magnetic interaction-free and ultrafast ferrimagnetic applications. [ABSTRACT FROM AUTHOR]

Reservoir computing is a brain heuristic computing paradigm that can complete training at a high speed. The learning performance of a reservoir computing system relies on its nonlinearity and short-term memory ability. As physical implementation, spintronic reservoir computing has attracted considerable attention because of its low power consumption and small size. However, few studies have focused on developing the short-term memory ability of the material itself in spintronics reservoir computing. Among various magnetic materials, spin glass is known to exhibit slow magnetic relaxation that has the potential to offer the short-term memory capability. In this research, we have quantitatively investigated the short-term memory capability of spin cluster glass based on the prevalent benchmark. The results reveal that the magnetization relaxation of Co, Si-substituted Lu3Fe5O12 with spin glass behavior can provide higher short-term memory capacity than ferrimagnetic material without substitution. Therefore, materials with spin glass behavior can be considered as potential candidates for constructing next-generation spintronic reservoir computing with better performance. [ABSTRACT FROM AUTHOR]

We have explored some magnetic characteristics of a mixed spin-3/2 and spin-1 Ising ferrimagnetic square nanoparticle by utilising the finite cluster approximation. The influences of the core and surface shell couplings (Jc, Js), as well as the crystal fields (Dc, Ds) on the critical and compensation behaviour, were investigated. In the absence of crystal fields, a compensation point only exists if Jc is higher than the threshold core coupling J*c, where the dependence of J*c on Js is linear. By introducing the crystal fields, we found a variety of topologies of the compensation temperature with the possibility of double reentrance. In particular, the presence of the core crystal field Dc, according to the Js strength, may lead to one, two, or three compensation points. [ABSTRACT FROM AUTHOR]

Spintronic devices use spin instead of charge to process information and are widely considered as promising candidates for next-generation electronic devices. In past decades, the main motivation in spintronics has been to discover new mechanisms and novel material systems to improve both device performance and the application prospects of spintronics. Recently, researchers have found that ferrimagnetic materials—in which sublattices are coupled antiferromagnetically—offer an emerging platform for realizing high-density, high-speed, and low-power-consumption memory and logic functions. Within such a ferrimagnetic class, vanishing magnetization and ultrafast magnetic dynamics can be achieved by adjusting chemical composition and temperature, among other parameters. Meanwhile, unlike for antiferromagnets, conventional electrical read–write methods remain suitable for ferrimagnets, which is beneficial for applications. In this review, an abundant class of ferrimagnets including oxides and alloys is surveyed, and unique magnetic dynamics and effective methods for manipulating the magnetic states of ferrimagnets are discussed. Finally, novel storage and computing devices based on ferrimagnets are considered, as there are some challenges to be addressed in future applications of ferrimagnets. [ABSTRACT FROM AUTHOR]

In this work, the magnetothermal characteristics and magnetocaloric effect in YFe3 and HoFe3 compounds are calculated as function of temperature and magnetic field. These properties were investigated using the two-sublattice mean field model and the first-principles DFT calculation using the WIEN2k code. The two-sublattice model of the mean-field theory was used to calculate the temperature and field-dependences of magnetization, magnetic heat capacity, magnetic entropy, and the isothermal change in entropy ∆Sm. We used the WIEN2k code to determine the elastic constants and, subsequently, the bulk and shear moduli, the Debye temperature, and the density-of-states at Ef. According to the Hill prediction, YFe3 has bulk and shear moduli of roughly 99.3 and 101.2 GPa respectively. The Debye temperature is ≈ 500 K, and the average sound speed is ≈ 4167 m/s. In fields up to 60 kOe and at temperatures up to and above the Curie point for both substances, the trapezoidal method was used to determine ∆Sm. For instance, the highest ∆Sm values for YFe3 and HoFe3 in 30 kOe are approximately 0.8 and 0.12 J/mol. K, respectively. For the Y and Ho systems, respectively, the adiabatic temperature change in a 3 T field decreases at a rate of around 1.3 and 0.4 K/T. The ferro (or ferrimagnetic) to paramagnetic phase change in these two compounds, as indicated by the temperature and field dependences of the magnetothermal and magnetocaloric properties, ∆Sm and ∆Tad, is a second-order phase transition. The Arrott plots and the universal curve for YFe3 were also calculated and their features give an additional support to the second order nature of the phase transition. [ABSTRACT FROM AUTHOR]

Manipulation of exchange bias (EB) via spin-current-induced spin–orbit torque (SOT) is of great importance in developing full electric control spintronic devices. Here, we report on SOT-dominant manipulation of the interfacial antiferromagnetic spins and the related perpendicular EB (PEB) in the IrMn/Co1-xTbx (CoTb) bilayers with various Tb contents. No matter the magnetization of the ferrimagnetic CoTb layer is Co-dominant or Tb-dominant; all the samples were perpendicularly magnetized, and spontaneous PEB could be established during the isothermal crystallization of the IrMn layer. The SOT-induced EB switching could be accomplished with assistance of an in-plane or out-of-plane external magnetic field, associated with a monotonic reduction of the EB switching fraction by increasing x. This phenomenon is attributed to weakening of the interfacial exchange coupling between the CoTb and IrMn layers as x is increased. These findings provide a way to design high energy-efficient spintronic devices by employing the antiferromagnet/ferrimagnet bilayers, which may have weak stray field and strong robustness in contrast to commonly used heavy-metal/ferromagnet/antiferromagnet trilayers. [ABSTRACT FROM AUTHOR]

Band structure and topology of magneto-spin–orbit graphene is investigated using the proposed tight-binding model that incorporates both Rashba and sublattice-resolved collinear exchange couplings in a generic ferrimagnetic (FIM) setting for in-plane and out-of-plane magnetization directions. The resulting band structures were analyzed for possibilities to extract the strengths of exchange and Rashba couplings from experimental spin-resolved ARPES measurements of the valley gaps and π -state spin-splittings. It was shown that the topologically trivial in-plane FIM situation admits simple expressions for these quantities, whereas the out-of-plane FIM, which admits a nontrivial band topology, is harder to analyze. The obtained topological phase diagrams for the out-of-plane FIM case show that the anomalous Hall conductance is quite stable with respect to the antiferromagnetic (AFM) interaction, which tends to interfere with the QAHE phase; moreover, the topological phase transition has a rather smooth character with respect to the AFM coupling strength. [ABSTRACT FROM AUTHOR]

Bimagnetic nanoparticles show promise for applications in energy efficient magnetic storage media and magnetic device applications. The magnetic properties, including the exchange bias of nanostructured materials can be tuned by variation of the size, composition, and morphology of the core vs overlayer of the nanoparticles (NPs). The purpose of this study is to investigate the optimal synthesis routes, structure and magnetic properties of novel CoO/NiFe2O4 heterostructured nanocrystals (HNCs). In this work, we aim to examine how the size impacts the exchange bias, coercivity and other magnetic properties of the CoO/NiFe2O4 HNCs. The nanoparticles with sizes ranging from 10 nm to 24 nm were formed by synthesis of an antiferromagnetic (AFM) CoO core and deposition of a ferrimagnetic (FiM) NiFe2O4 overlayer. A highly crystalline magnetic phase is more likely to occur when the morphology of the core-overgrowth is present, which enhances the coupling at the AFM-FiM interface. The CoO core NPs are prepared using thermal decomposition of Co(OH)2 at 600 °C for 2 hours in a pure argon atmosphere, whereas the HNCs are obtained first using thermal evaporation followed by hydrothermal synthesis. The structural and morphological characterization made using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and scanning electron microscopy (SEM) techniques verifies that the HNCs are comprised of a CoO core and a NiFe2O4 overgrowth phase. Rietveld refinement of the XRD data shows that the CoO core has the rocksalt (Fd3 m) crystal structure and the NiFe2O4 overgrowth has the spinel (C12/m1) crystal structure. SEM-EDS data indicates the presence and uniform distribution of Co, Ni and Fe in the HNCs. The results from PPMS magnetization measurements of the CoO/NiFe2O4 HNCs are discussed herein. [ABSTRACT FROM AUTHOR]

We have carried out joint theoretical and experimental investigations of three Heusler compounds CoMoFeAl, CoMo0.5Fe1.5Al, and Co1.5Mo0.5FeAl. Our first-principle calculations show that all three compounds show either ferro- or ferrimagnetic order with CoMoFeAl and CoMo0.5Fe1.5Al exhibiting high spin polarization of almost 80%. The investigated samples were prepared using arc melting and high vacuum annealing. All the samples show cubic crystal structure with disorder. The parent compound CoMoFeAl shows a small saturation magnetization of 12 emu/g, and a Curie temperature of 440 K. The other two compounds, namely, Co1.5Mo0.5FeAl and CoMo0.5Fe1.5Al, show much higher saturation magnetizations of 62 emu/g and 59 emu/g, and substantially higher Curie temperatures of 950 K and 780 K, respectively. [ABSTRACT FROM AUTHOR]

In this work, we investigate the synthesis, along with the structural and magnetic properties, of novel Mn-Co-NiO-based heterostructured nanocrystals (HNCs). The objective is to develop novel, well-structurally ordered inverted antiferromagnetic (AFM) NiO–ferrimagnetic (FiM) spinel phase overgrowth HNCs. Inverted HNCs are particularly promising for magnetic device applications because their magnetic properties are more easily controlled by having well-ordered AFM cores, which can result in magnetic structures having large coercivities, tunable blocking temperatures, and other enhanced magnetic effects. The synthesis of the HNCs is accomplished using a two-step process: In the first step, NiO nanoparticles are synthesized using a thermal decomposition method. Subsequently, Mn-Co overgrowth phases are grown on the NiO nanoparticles via hydrothermal nanophase epitaxy, using a fixed pH level (∼5.3) of the aqueous medium. This pH level was selected based on previous work in our laboratory showing that NiO/Mn3O4 HNCs of constant size have optimal coercivity and exchange bias when synthesized at a pH of 5.0. The crystalline structure and gross morphology of the Mn-Co-NiO-based HNCs have been analyzed using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques, respectively. Analysis using these techniques shows that the HNCs are composed of a NiO core and a CoMn2O4 overgrowth phase. Rietveld refinement of XRD data shows that the NiO core has the rocksalt (Fm 3 ̄ m) cubic crystal structure and the CoMn2O4 overgrowth has the spinel (I41/amd) crystal structure. Moreover, an increased relative amount of the CoMn2O4 overgrowth phase is deposited with decreasing NiO core particle size during the synthesis of the HNCs. The results from PPMS magnetization and high-resolution transmission electron microscopy (HRTEM) characterization of the Mn-Co-NiO-based HNCs are discussed herein. [ABSTRACT FROM AUTHOR]

Ferrimagnetic substance-based Zn0.4Alx@Ni0.6-xFe2O4 (x = 0.0, 0.02, 0.04, 0.06, and 0.08) nanocomposite system was prepared by two-step seed implant polyacrylamide sol–gel method. The structural and frequency-dependent sensitivity of soft magnetic core materials was optimized by the substitution of Al3+ ions. The nonstoichiometric of the constituents has caused by the consisting of a small amount of two secondary phases (Zn-oxide and Zn-Al-oxide) which have been detected from the short intensity of XRD peaks using the Rietveld refinement program. The replacement of Ni2+ ions by Al3+ ions plays a major role in the rearrangements of Ni2+ and Fe3+ ions between octahedral A and tetrahedral B sites and is lead to optimization of magnetic behavior and impedance response. The maximum coercivity (493.73 Oe) and saturation magnetization (58.26 emu/g) observed at x = 0.08 and 0.02, respectively. The resulting magnetic permeability shows that the value is enhanced up to 6.411% within 1 Oe of applied magnetic field. In addition, the impedance value reaches maximum of 1.49 × 105 Ω at sample x = 0.02, reduced to minimum of 4.8 × 103 Ω at x = 0.08. The magnetic sensitivity of ZnAl-NiFe2O4-based core materials at room temperature under 0–5 log f with 0.01 T magnetic field has also been investigated. The magneto-impedance results can be used to substantiate the increase in sensitivity due to the rearrangement of Ni2+ and Fe3+ ions. [ABSTRACT FROM AUTHOR]

Nontrivial chiral spin textures with nanometric sizes and novel characteristics (e.g., magnetic skyrmions) are promising for encoding information bits in future energy‐efficient and high‐density spintronic devices. Because of antiferromagnetic exchange coupling, skyrmions in ferrimagnetic materials exhibit many advantages in terms of size and efficient manipulation, which allow them to overcome the limitations of ferromagnetic skyrmions. Despite recent progress, ferrimagnetic skyrmions have been observed only in few films in the presence of external fields, while those in ferrimagnetic bulks remain elusive. This study reports on spontaneously generated zero‐field ground‐state magnetic skyrmions and their subsequent transformation into traditional magnetic bubbles via intermediate states of (bi‐)target bubbles during a magnetic anisotropy change in the rare‐earth ferrimagnetic crystal DyFe11Ti. Spontaneous reversible topological transformation driven by a temperature‐induced spin reorientation transition is directly distinguished using Lorentz transmission electron microscopy. The spontaneous generation of magnetic skyrmions and successive topological transformations in ferrimagnetic DyFe11Ti are expected to advance the design of topological spin textures with versatile properties and potential applications in rare‐earth magnets. [ABSTRACT FROM AUTHOR]

The ferrimagnetic-ferromagnetic-ferrimagnetic quaternary alloy consisting of the spins S i A = 1 , S j B = 3 / 2 , S j C = 5 / 2 and S j D = 2 in the form of A B p C q D r with B, C and D being the possible nearest-neighbors of A with the probabilities p, q and r, respectively, is investigated in terms of the mean field theory (MFT) based on the Bogoliubov inequality for free energy. The thermal behaviors of magnetizations belonging to the individual spins and total magnetization are examined in detail to map the possible phase diagrams on various planes. It was found that the model only exhibits second-order phase transitions in addition to one compensation temperature for appropriate values of the system parameters. In order to support the existence of the compensation temperatures, we have also carried out the Monte Carlo (MC) simulations and an agreement was shown with the predicted result of the MFT approach. We have also analyzed the effects of the bilinear interaction parameter between type-A atoms J A A and the exchange interaction parameter ratio R = J A X / | J A B | ( J A X is the bilinear interaction parameter between type-A atoms and type-X atoms with X = C or D) on compensation temperatures. Our findings are compared to those reported in the literature and suitable agreements are observed. [ABSTRACT FROM AUTHOR]

We studied some magnetic behaviors of the Ising model in a single-wall mixed spin (σ = ½, S = 1) triangular nanotube using the effective field theory with correlations (EFTC), and the differential operator technique (DOT). The effects of exchange interactions as well as the temperature and the applied field on the magnetic properties of the nanotube, such as isotherm and spontaneous magnetizations, were carefully analyzed. We demonstrated that the low-temperature behavior of the magnetization is very sensitive to the exchange interactions involved, especially in the case of competitional couplings. Besides the phase diagram, unusual phenomena have been discovered, especially for opposite exchange interactions where magnetization plateaus and frustration are observed. Several forms of ferrimagnetism have been revealed for judicious choices of exchange and single-ion anisotropy. One of the most notable effects is the occurrence of magnetization jumps and fractional plateaus due to both the geometry and the competition between exchange couplings, on the one hand, and the applied magnetic field, on the other hand. Such plateaus could provide a path toward potential applications of functional ferrimagnets in spintronics and device regulation. [ABSTRACT FROM AUTHOR]

We improve thermal tolerance of a Co/Pt based synthetic ferrimagnetic (SyF) reference layer in a CoFeB/MgO-based perpendicular anisotropy magnetic tunnel junction by employing a surface modification treatment (SMT) using Ar plasma on a Pt buffer layer underneath the SyF layer. A higher perpendicular anisotropy and more robustness against annealing for the SyF reference layer is observed by the employment of SMT. From the cross-sectional scanning transmission electron microscope of the magnetic tunnel junction and atomic force microscopy on the Pt buffer layer, SMT has no significant effect on the surface roughness of the Pt buffer layer. On the other hand, X-ray diffraction analysis reveals that SMT increases the lattice spacing of the Pt buffer layer and shrinks that of the Co/Pt multilayer, which are maintained after annealing at 400 °C. Those structural changes could lead to the improvement of perpendicular anisotropy and thermal tolerance against annealing. A high-resolution Rutherford backscattering analysis reveals that Ar ions used for SMT penetrate to the Pt buffer layer, resulting in variation of the lattice spacing for the Pt buffer layer and Co/Pt multilayer. In addition, suppression of Fe diffusion from the CoFeB reference layer to the bottom Co/Pt multilayer is observed by using energy dispersive X-ray spectrometry, which also contributes to the higher thermal tolerance against annealing. The present observation reveals that the employment of SMT enables one to obtain both high perpendicular magnetic anisotropy and high robustness against annealing through crystallographic change of the Co/Pt multilayer and suppression of Fe diffusion from CoFeB layer into the Co/Pt multilayer. [ABSTRACT FROM AUTHOR]

We present a simple semiclassical model to sustain that in europium chalcogenides (EuX), Faraday rotation (FR) in the transparency gap is proportional to the magnetization of the sample, irrespective of the material's magnetic phase, temperature, or applied magnetic field. The model is validated by FR and magnetization measurements in EuSe in the temperature interval 1.7–300 K, covering all EuSe magnetic phases (paramagnetic, antiferromagnetic type I or type II, ferrimagnetic, and ferromagnetic). Furthermore, by combining the semiclassical model with the explicit electronic energy structure of EuX, the proportionality coefficient between magnetization and FR is shown to be dependent only on the wavelength and the bandgap. Due to its simplicity, the model has didactic value; moreover, it provides a working tool for converting FR into magnetization in EuX. The possible extension of the model to other intrinsic magnetic semiconductors is discussed. [ABSTRACT FROM AUTHOR]

As an electrode material with reported ferrimagnetic properties, the NiCo2O4 film exhibits critical electrical transport properties under a magnetic field as well as a magnetic microstructure. In this study, epitaxial NiCo2O4 films were prepared on LaAlO3 (100) substrates, and the effects of growth temperature on the magnetic and electrical transport properties of the films were investigated. Negative magnetoresistance was observed in the films due to the local spin effect. The NiCo2O4 films demonstrated a topological Hall effect, which is closely related to short-range magnetic order and a noncoplanar magnetic structure in NiCo2O4 films. The results indicate that there are two types of spin frustration in the NiCo2O4 structure. One is a diamond lattice composed of tetrahedral site cations, while the other is a triangular lattice structure formed by the edge-shared octahedral cations. For the NiCo2O4 (100) films, the sign of the ordinary Hall coefficient reverses by decreasing the measurement temperature, indicating that the carrier type changes from p to n. [ABSTRACT FROM AUTHOR]

A ferrimagnet (FiM) has small domains consisting of oppositely polarized and unequal magnetic moments. Oppositely polarized magnetic moments have strong exchange coupling between them resulting in robust torque in FiM called bulk torque. Due to the strong bulk torque, magnetic moments in FiM do not precess around the switching axis for a long time unlike ferromagnets (FMs) leading to faster switching speed compared to FM. In this paper, we propose and model the switching of FiM (CoTb) with spin current injection from heavy metal with strong spin Hall effect (SHE) such as Pt. We carry out ab initio calculation of the Dzyaloshinskii-Moriya interaction (DMI) at the FiM(CoTb)/heavy metal(Pt) interface using spin polarized relativistic Korringa-Kohn-Rostoker (KKR) Green's function method. We compute the exchange coupling among the magnetic moments inside the CoTb layer and model how the spin-orbit torque (SOT) along with the bulk torque can efficiently switch the FiM. Then, we consider a ferrimagnet based magnetic tunnel junction (FMTJ) with SHE metal. We perform a comprehensive simulation and performance analysis of FiM(CoTb)/MgO/CoFeB and FiM(CoTb)/MgO/FiM(CoTb) FMTJs with Pt underlayer. Using non-equilibrium Green's function (NEGF) formalism, we calculate the tunneling magnetoresistance (TMR) of the proposed FMTJs at room temperature. Furthermore, the importance of thickness in CoTb magnetization dynamics is shown using our FiM magnetization simulation framework. We analyze and show that the CoTb based FMTJ has large switching energy barrier to ensure thermal stability. Finally, we show the performance comparison (TMR, write performance and power consumption) between our proposed FMTJs and FM based MTJ and our simulation exhibits that for picosecond range switching speed, FMTJ is ∼ 25 times more energy efficient than FM based MTJ. [ABSTRACT FROM AUTHOR]

The effect of partial substitution of Ge for Sb on the first-order ferrimagnetic (FRI)–antiferromagnetic (AFM) transition in Mn 2 Sb has been studied. It shows that the transition temperature (T t) can be tuned between 119 K and 271 K by substituting 2.5%–10% Ge at Sb sites in Mn 2 Sb. The variation of density of state at the Fermi level N(E f) with Ge substitution shows that dN(E)/dE is positive at E f in the AFM state. With the application of a magnetic field, T t shifts to low temperature, which results in a giant negative magnetoresistance (MR) reaching a value of 70% for 2.5% substitution. Our results show that FRI to AFM transformation during cooling stops around 35 K, even though it remains incomplete. This, along with the nonmonotonic variation of lower critical field, open loop in isothermal MR, and increasing difference in zero field cooled warming and field cooled warming resistivity with increasing magnetic field, shows that the FRI to AFM transition is kinetically arrested in the case of 2.5% Ge substitution. [ABSTRACT FROM AUTHOR]

Antiferromagnetic magnetization dynamics is more effective than ferromagnetic magnetization; however, it is extremely complex. Rare earth (RE) ferrimagnets, on the other hand, have tunable magnetization with associated negative exchange interaction in sublattices. Here, we study different RE-Fe ferrimagnets while changing the RE-content. We obtain various magnetic properties like saturation magnetization MS, coercivity HC, magnetic anisotropy energy constant Ku, exchange coupling constant λ, and compensation temperature Tcomp for different RE compositions. We suggest that along with MS and HC, λ is another important parameter that is easy to measure and has information that is similar to that in the spin-orbit torque effective field and the canting angle. [ABSTRACT FROM AUTHOR]

Structural and magnetic properties of the spinel compound, Li0.5FeCr1.5O4, have been investigated using dc magnetization, neutron depolarization, and neutron diffraction techniques. DC magnetization measurement at 200 Oe has revealed a ferrimagnetic ordering at 417 K and a negative magnetization state between the two compensation temperatures (TComp) of 244 and 256 K. TComp varies with an applied magnetic field and two TComp merge at 256 K for magnetic fields ≥ 500 Oe. The existence of zero domain magnetization around TComp is evident from full recovery of the transmitted neutron beam polarization in a neutron depolarization study. The Rietveld refinement of the neutron diffraction pattern at 430 K reveals that the compound possesses a face centred cubic structure with Fe0.81Li0.19 and Cr1.5Li0.31Fe0.19 as cation distributions at the tetrahedral and octahedral sites, respectively. A temperature dependent neutron diffraction study reveals that the net magnetic moment changes sign near 265 K, across the spin compensation temperature. Both neutron diffraction and mean field calculation show that an asymmetric variation of the sublattice moments as a function of temperature yields a dominance of the ordered tetrahedral site moment over the octahedral site moment below TComp, and vice versa above TComp, and gives a microscopic understanding of the observed magnetization reversal phenomenon. The achieved understanding of magnetization compensation and the high coercivity near TComp have implications for possible use of such ferrimagnetic materials with finite spin polarization as effective spin polarizers/analyzers in spintronic devices. [ABSTRACT FROM AUTHOR]

A theoretical model based on the Landau-Lifshitz-Bloch equation is developed to study the effect of damping-like spin-orbit torque in ferrimagnets, which can capture many experimental findings. For example, the sample changes from Gd to FeCo dominate by increasing temperature, the damping-like spin-orbit torque has a peak at the magnetization compensation temperature, and angular-momentum compensation temperature increases as a function of Gd concentration. In contrast to the ferromagnet system, the switching trajectory in ferrimagnets is found to be precession free. The two sublattices are not always collinear, which produce a large exchange field affecting the magnetization dynamics. The study of material composition shows the existence of an oscillation region at intermediate current density, induced by the nondeterministic switching. Compared to the Landau-Lifshitz-Gilbert model, our developed model based on the Landau-Lifshitz-Bloch equation enables the systematic study of the spin-torque effect and the evaluation of ferrimagnet-based devices. [ABSTRACT FROM AUTHOR]

High-frequency coaxial waveguide measurements are used to evaluate composition- and frequency-dependent complex permittivities and permeabilities of polycrystalline ferroelectric and ferrimagnetic ceramics. Material dielectric and magnetic property measurements were performed on ferroelectric barium titanate (BaTiO3) and ferrimagnetic yttrium iron garnet (YIG), with the upper measurement frequency bound below gyromagnetic resonance of YIG. These polycrystalline materials were chosen because of their widespread use in voltage- and magnetic field-tunable devices. Wideband frequency material measurements were used to predict dielectric and magnetic properties of various two-phase composite media incorporating BaTiO3 and YIG. Two effective medium theories were used: an asymmetric, modified Maxwell-Garnett type and a symmetric Bruggeman model. The Bruggeman effective medium model is extended to include three-phases. The three-phase Bruggeman predictive model is employed when controlled porosity is introduced into the composite and when two component phases are combined with polytetrafluoroethylene. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions (MTJs) exhibit a great profusion of unique functional properties, such as nonvolatility, scalability, high endurance, and low power consumption. For this reason, they have been widely investigated in spin-based logic and memory devices. Compared with conventional in-plane MTJs, perpendicular MTJs (pMTJs) enable lower critical switching current and higher integration density. So far, CoFeB/MgO structures with interface-induced perpendicular magnetic anisotropy (PMA) are the most common ferromagnetic (FM) electrodes in pMTJs, whereas their relatively weak interfacial PMA restricts further development of device nodes. In the past decade, perpendicularly magnetized MnxGa binary alloys, including FM L10-MnGa and ferrimagnetic D022-Mn3Ga, have drawn intense attention for serving as a promising magnetic electrode in various MTJ stacking structures because of their large PMA, high spin polarization, and small magnetic damping constant. From an application perspective, MTJs with ultrathin MnxGa electrode show merits in developing high-density magnetic memory, high-frequency spin-torque oscillators, and tunneling magnetoresistance effect-based high-field sensors. Herein, the aim is to provide a comprehensive review of recent progress in perpendicularly magnetized MnxGa-based MTJs. The conclusions and future prospects are also given to inspire more in-depth research and advance the practical applications. [ABSTRACT FROM AUTHOR]

Ferrimagnets are the magnetic materials with the fastest current-induced dynamics reported so far. Among them, rare-earth transition-metal (RE-TM) alloys offer a fertile playground for studying the behavior of multi-sublattice systems with tunable composition and magnetic interactions. This review provides a survey of the magnetic dynamics excited by current-induced spinorbit torques (SOTs) in RE-TM ferrimagnets coupled to heavy-metal layers. It summarizes the magnetic properties of RE-TM alloys and discusses how interfacial SOTs result in efficient magnetization switching and fast domainwall motion close to the magnetization and angular momentum compensation points. Recent work shows that the switching is a multiphase process affected by significant stochastic fluctuations. However, strong SOTs results in fast and deterministic sub-ns switching with minimal energy dissipation. In addition, the RE and TM magnetizations can respond asynchronously to SOTs during the reversal. This asynchronous dynamics pinpoints the different strength of the SOTs acting on the two sublattices and challenges the usual assumption of rigid inter-sublattice antiferromagnetic coupling. Overall, the ability to tailor the timescale and reversal mode of RE-TM alloys allows for optimizing the speed of ferrimagnetic spintronic devices and provides insight into the current-induced transfer of angular momentum in systems with synergistic ferromagnetic and antiferromagnetic interactions. [ABSTRACT FROM AUTHOR]

Lately, the development of green chemistry methods with high efficiency for metal nanoparticle synthesis has become a primary focus among researchers. The main goal is to find an eco-friendly technique for the production of nanoparticles. Ferro- and ferrimagnetic materials such as magnetite (Fe3O4) exhibit superparamagnetic behavior at a nanometric scale. Magnetic nanoparticles have been gaining increasing interest in nanoscience and nanotechnology. This interest is attributed to their physicochemical properties, particle size, and low toxicity. The present work aims to synthesize magnetite nanoparticles in a single step using extracts of green lemon Citrus Aurantifolia residues. The results produced nanoparticles of smaller size using a method that is friendlier to health and the environment, is more profitable, and can be applied in anticorrosive coatings. The green synthesis was carried out by a co-precipitation method under variable temperature conditions. The X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) characterization showed that magnetite nanoparticles were successfully obtained with a very narrow particle size distribution between 3 and 10 nm. A composite was produced with the nanoparticles and graphene to be used as a surface coating on steel. In addition, the coating's anticorrosive behavior was evaluated through electrochemical techniques. The surface coating obtained showed good anticorrosive properties and resistance to abrasion. [ABSTRACT FROM AUTHOR]

Perovskite-type ABO3 oxides show a number of cation-ordered structures, which have significant effects on their properties. The rock-salt-type order is dominant for B cations, and the layered order for A cations. In this work, we prepared a new perovskite-type oxide, Sm2CuMn(MnTi3)O12, with a rare columnar A-site order using a high-pressure, high-temperature method at about 6 GPa and about 1700 K. Its crystal structure was studied with synchrotron powder X-ray diffraction. The compound crystallizes in space group P42/nmc (No. 137) at room temperature with a = 7.53477 Å and c = 7.69788 Å. The magnetic properties of the compound were studied with dc and ac magnetic susceptibility measurements and specific heat. Spin-glass (SG) magnetic properties were found with TSG = 7 K, while specific heat, in the form of Cp/T, showed a strong, very broad anomaly developing below 20 K and peaking at 4 K. The dielectric constant of Sm2CuMn(MnTi3)O12 was nearly frequency and temperature independent between 8 K and 200 K, with a value of about 50. Cu2+ doping drastically modified the magnetic and dielectric properties of Sm2CuMn(MnTi3)O12 in comparison with the parent compound Sm2MnMn(MnTi3)O12, which showed a long-range ferrimagnetic order at 34–40 K. The antisite disorder of Cu2+ and Mn2+ cations between square-planar and octahedral sites was responsible for the SG magnetic properties of Sm2CuMn(MnTi3)O12. [ABSTRACT FROM AUTHOR]

The current study examines the structural, surface morphology, electrical, optical, and magnetic properties of [Co(1-x)Scx][Cr2][O4] (x = 0, 0.01, 0.03, 0.05, 0.07) prepared by combustion method. XRD (X-ray diffraction) and Raman spectra were utilized to confirm phase and structural. SEM (scanning electron microscopy) micrographs were utilized for the analysis of the surface morphology. AC conductivity and dielectric characteristics were utilized to investigate the electrical properties. UV–Vis DRS (UV–Vis diffuse reflectance spectroscopy) was used to investigate the optical characteristics. The development of spinel cubic structure is confirmed by XRD. The hopping lengths increase as the Sc3+ ion concentration rises. The extremely porous nature may be seen in all SEM images. The Koop's phenomenological theory and hopping mechanism were utilized to explain dielectric properties. At higher frequencies, all samples have good AC conductivity and a low dielectric loss tangent. Optical experiments were conducted using a UV–Visible diffuse reflectance spectrometer to assess the energy gap and absorbance bands. The decrease in the energy gap as Sc3+ concentration rises could be explained by an increase in the lattice parameter due to an increase in Sc3+ concentration. The dc-susceptibility study reveals two magnetic transitions such ferrimagnetic (FIM) order transition below Curie temperature (Tc) and spiral spin order transition at spiral transition temperature (Ts). The scandium-doped [Co][Cr2][O4] samples show negative magnetization below compensation temperature (Tcomp). The obtained results from M-H loop at 25 K, 95 K, and 300 K agree well with the magnetic transitions obtained from the temperature-dependent susceptibility study. [ABSTRACT FROM AUTHOR]

The magnetic properties and phase diagrams of a ferrimagnetic cylindrical Ising nanotube with spin-1/2 core and spin-3/2 shell are studied using mean-field approximation and Monte Carlo simulation. The effects of shell and core-shell interface exchange couplings and crystal field on the magnetic properties of the system are examined. For some physical parameters, the critical and compensation behaviors are highlighted and first-order phase transitions are observed in the ferrimagnetic ordered region at low temperatures. A comparison between the two methods was performed. [ABSTRACT FROM AUTHOR]

The structural, magnetic, and dielectric properties of a series of Ni2+ substituted cobalt nanoferrite particle samples with the composition Co1−xNixFe2O4 (where x = 0.0 ≤ x ≤ 1.0) synthesized by using the sol-gel auto combustion route are presented in this report. The electromagnetic interference shielding of Co1−xNixFe2O4/PVA nanocomposite films has been determined in the microwave X-band (8.2–12.4 GHz) frequencies. X-ray analysis revealed the single-phase formation of nickel-substituted cobalt nanoferrite samples. The decreasing trend of lattice parameters with Ni2+ substitution indicates the incorporation of Ni2+ into the crystal structure, obeying Vegard's law. FTIR showed the absorption bands at 560–590 cm−1 ( v 1 ) and 390–400 cm−1 ( v 2 ) were attributed to (A-site) tetrahedral and (B-site) octahedral groups complex, respectively which confirm the spinel structure of the samples. Field emission scanning electron microscopy showed agglomerated grains of different sizes and shapes in the morphological observation. EDS reveals the chemical composition of the prepared samples. TEM analysis revealed that the synthesized particles were nearly monodisperse, show to be roughly spherical in shape, and have a polycrystalline nature. The dielectric constant and loss tangent (tanδ) is found to decrease with increasing frequency which shows normal behavior for ferrimagnetic materials. The magnetic properties determined using VSM have substantially changed with the substitution of Ni2+ ions. The saturation magnetization and the experimentally magnetic moment are observed to decrease with an increase in Ni2+ content x. A series of Co1−xNixFe2O4/PVA nanocomposite films are prepared by applying simple, rapid, and inexpensive methods for EMI shielding materials. The vector network analyzer data were used to evaluate the electromagnetic interference (EMI) shielding properties of the Co1−xNixFe2O4/PVA samples. At 9.2 GHz, a study of reflection loss showed a minimum reflection loss (RL) of −32.08 dB. Also, the synthesized Co1−xNixFe2O4/PVA nanocomposite samples show improved performance for EMI efficiency which proves the utility of this doping. With this low RL value, the results and techniques also promise a simple, effective approach to achieve light-weight Co1−xNixFe2O4/PVA nanocomposite films and make it excellent microwave absorbers, capable of working at gigahertz frequencies for application potentials in EMI shielding material, communication, radar stealth technology, and electronic warfare. [ABSTRACT FROM AUTHOR]

Fe doped Sr 2 RuMnO 6 (SRMO) double perovskites (Sr 2 RuMn 1-x Fe x O 6 , x = 0, 0.1, 0.2 and 0.3) were prepared by solid-state route. Both x-ray diffraction and Raman spectroscopy were performed to investigate the crystal structure of the synthesized double perovskites. Rietveld refinement of the x-ray diffraction patterns confirmed a phase transition from tetragonal to cubic space group as a function of doping concentration of iron. Raman spectroscopy at room temperature and group theory analysis revealed the phonon modes associated with the space group of the samples. The temperature dependent Raman spectroscopy showed an anharmonic behaviour of the phonon modes of the Fe doped SRMO samples. The temperature evolution of the phononic modes in the range of 300 K–620 K is predominantly influenced by the lattice degrees of freedom. The presence of several oxidation states Mn (2+, 3+ and 4+) and Fe (3+ and 4+) was confirmed by an X-ray photoemission spectroscopy analysis of the highest doped sample (x = 0.3). The magnetic properties measurements showed that the samples were completely paramagnetic at room temperature. The samples exhibit antiferromagnetism at very low temperatures and we conclude that they exhibit ferrimagnetic ground state in the mid temperature region. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions are meta-stable spin structures that naturally emerge in magnetic materials. While a vast amount of effort has gone into the study of their properties, their counterpart of opposite topological charge, the anti-skyrmion, has not received as much attention. We aim to close this gap by deploying Monte Carlo simulations of spin-lattice systems in order to investigate which interactions support anti-skyrmions, as well as skyrmions of Bloch and Néel type. We find that the combination of ferromagnetic exchange and Dzyaloshinskii–Moriya (DM) interactions is able to stabilize each of the three types, depending on the specific structure of the DM interactions. Considering a three-dimensional spin lattice model, we provide a finite-temperature phase diagram featuring a stable anti-skyrmion lattice phase for a large range of temperatures. In addition, we also shed light on the creation and annihilation processes of these anti-skyrmion tubes and study the effects of the DM interaction strength on their typical size. [ABSTRACT FROM AUTHOR]

We investigated the dynamic phase transitions (DPTs) in the mixed spin (2, 5/2) Blume-Emery-Griffiths model with repulsive biquadratic interaction in the presence of a time-varying magnetic field. We used the path probability method to obtain the set of the dynamic equations. We numerically solved these dynamic equations to characterize the nature of first- and second-order phase transitions and to find the DPT temperatures as well as obtain the phases in the system. We constructed the dynamic phase diagrams (DPDs) in reduced temperature and amplitude of oscillating magnetic field plane. We observed that the DPDs display richer, complex and more topological various type of phase diagrams. In particular, DPDs exhibit the disordered phase, antiquadrupolar or staggered phase, six different ferrimagnetic phases, three different nonmagnetic phases, and numerous mixed phases. DPDs also display two dynamic tricritical points for only smaller values of crystal-field interactions, multiple critical end and double critical end points, one zero-temperature critical point, one inverse critical end point, and a quadruple point depending on interaction parameters. The system always shows the reentrant behaviors for the higher values of magnetic field amplitude, but it does not exhibit the dynamic tricritical behavior for higher values of crystal-field parameter. [ABSTRACT FROM AUTHOR]

By employing a melt‐sintering method, we prepared a new type of ferrimagnetic glass–ceramic foam (FGCF) using ferrimagnetic glass–ceramic and foaming agent SrCO3. The ferrimagnetic glass–ceramics were fabricated based on pyrite slag by a melt‐quenching method. The effects of foaming agent content, sintering temperature and time on microstructure, magnetic properties, microwave absorption performance, compressive strength, and thermal conductivity of the as‐obtained FGCF were analyzed. This foaming process at 1100°C for 40 min with 3‐wt% SrCO3 provided an FGCF with a bulk density of.693 g/cm3, a porosity of 63.60%, a specific saturation magnetic moment of 5.2 A m2/kg, a compressive strength of 2.61 MPa, a thermal conductivity of.241 W/(m K), and the calculated reflection loss of −12.1 dB for a layer thickness of 9 mm. [ABSTRACT FROM AUTHOR]

The electronic structure, magneto-optic properties of two systems: Sr2FeReO6 and Sr2CrWO6 are investigated using the FPLAPW employing the GGA approximation. Our results show that the two systems have a half metallic character. The obtained magnetic moments indicate that first is ferromagnetic, while the second is ferrimagnetic. The DFT was used to calculate the magnetic moment and the exchange energies. The obtained results are used in Monte Carlo simulations (MCS) to determine some magnetic parameters such as: magnetization, susceptibility, relative cooling power, adiabatic change in temperature and magnetic entropy under temperature effect. [ABSTRACT FROM AUTHOR]

Fluorescence detection is currently one of the commonly used techniques worldwide. Through this work, the preparation and optical properties of an interesting composite material are discussed. It is shown that encapsulating cobalt spinel ferrite (CoFe2O4), obtained by the sol-gel autocombustion method, into poly[diphenyl-co-methyl(H)]silane matrix leads to fluoromagnetic particles (PSCo) with intriguing optical properties. Transmission electron microscopy, combined with energy-dispersive X-ray analysis, showed 500 nm large spherical structures containing a core (around 400 nm in diameter) composed of magnetic ferrite particles, surrounded by a thin layer of semiconductive fluorescent polymer. The as-obtained material exhibited ferrimagnetic properties. The FTIR spectrum confirmed that the Si-H functionality of the polysilane was preserved. UV spectroscopy combined with molecular modeling studies indicated that the magnetic core had a strong influence on the intramolecular electron transitions characteristic of the σ-conjugated polysilane. Further analysis by steady-state fluorescence spectroscopy revealed that the internal magnetic field strongly enhances the polysilane emission. This property will be further investigated in the future in order to develop new detection devices. [ABSTRACT FROM AUTHOR]

The ferrimagnetic nodal-line semiconductor Mn 3 Si 2 Te 6 , featuring a quasi-two-dimensional crystal structure, has attracted significant attention owing to its rich physical properties. Here, we systematically investigate the magnetic properties of its isostructural compound, Mn 3 Si 2 Se 6. The magnetism of this material is attributed to the Mn atoms, which exhibit antiferromagnetic interactions among the Mn atoms. The competition between antiferromagnetic exchange interactions results in an overall ferrimagnetic state, with a second-order transition from paramagnetic to ferrimagnetic occurring at 68 K. Critical exponents are derived using various common experimental techniques, including the modified Arrott plot, Kouvel-Fisher method, and critical isotherm analysis. The results indicate that the magnetism of Mn 3 Si 2 Se 6 closely aligns with the mean-field model, with critical exponents β , γ , and δ determined as 0.475(3), 1.059(3), and 3.20(1), respectively, at the critical temperature of 68.3(2) K. Moreover, the curves of the magnetic entropy change − Δ S M (T , H) exhibit a peak around T c , with − Δ S M max amounts to 4.61 (3.63) J kg−1 K−1 for H ∕∕ ab (∕∕ c) with a field change of 7 T. The estimated magnetic entropy value near T c through specific heat is remarkably saller than the expected spin entropy of Mn2+ ions, indicating the presence of short-range interactions in the paramagnetic region. • The competition exchange interactions result in an overall ferrimagnetic state in Mn 3 Si 2 Se 6. • Magnetism of Mn 3 Si 2 Se 6 aligns with the mean-field model. • Specific heat analysis reveals short-range interactions in Mn 3 Si 2 Se 6 's paramagnetic region. [ABSTRACT FROM AUTHOR]

We have investigated the laser induced ultrafast dynamics of Gd 4f spins at the surface of Co x Gd 100-x alloys by means of surface-sensitive and time-resolved dichroic resonant Auger spectroscopy. We have observed that the laser induced quenching of Gd 4f magnetic order at the surface of the Co x Gd 100-x alloys occur on a much longer time scale than that previously reported in "bulk sensitive" time-resolved experiments. In parallel, we have characterized the static structural and magnetic properties at the surface and in the bulk of these alloys by combining Physical Property Measurement System (PPMS) magnetometry with X-ray Magnetic Circular Dichroism in absorption spectroscopy (XMCD) and X-Ray Photoelectron spectroscopy (XPS). The PPMS and XMCD measurements give information regarding the composition in the bulk of the alloys. The XPS measurements show non-homogeneous composition at the surface of the alloys with a strongly increased Gd content within the first layers compared to the nominal bulk values. Such larger Gd concentration results in a reduced indirect Gd 4f spin-lattice coupling. It explains the "slower" Gd 4f demagnetization we have observed in our surface-sensitive and time-resolved measurements compared to that previously reported by "bulk-sensitive" measurements. • Characterization of electronic, magnetic and structural properties of ferrimagnetic CoGd amorphous alloys. • Gd 4f spin dynamics at the surface of CoGd alloys by means of Time-Resolved Dichroic Resonant Auger Spectroscopy. • Disparate Gd 4f ultrafast spin dynamics in CoGd alloys due to non-homogeneous in-depth composition. [ABSTRACT FROM AUTHOR]

Density Functional Theory (DFT) calculations are performed using full potential linearized augmented plane wave (FP-LAPW) method to study CoTiFeGe and Co 2 Fe 0.25 Mn 0.75- x Ti x Ge (x = 0, 0.25, 0.50, 0.75) systems through GGA and mBJ-GGA formalisms. The lattice equilibrium optimization was conducted to determine the stable magnetic phase state of these systems. It was found that the systems exhibit stability in a ferromagnetic nature, with the exception of the Co 2 Fe 0.25 Mn 0.75 Ge compound, which displays ferrimagnetic behavior. Electronic band structures and density of states for our systems show a half-metallic character using mBJ-GGA, except the Co 2 Fe 0.25 Mn 0.75 Ge system, which exhibits metallic behavior. Furthermore, the studied systems adhere to the Slater-Pauling rule condition for half-metallicity of alloys M tot = Z V -24. Optoelectronic properties have been analyzed using optical parameters, confirming semiconducting behavior. Optical reflections with minimal loss and the existence absorption are observed in the infrared and visible areas suggest that the studied systems are suitable for optoelectronic devices. Additionally, a comprehensive assessment of the thermodynamic properties of the systems was carried out to investigate their thermodynamical stability against temperature and pressure change. The transport properties of these systems were systematically investigated, revealing that our alloys present the poor thermoelectric matter. [Display omitted] • Study of thermoelectric and thermodynamic properties of two systems. • Ferromagnetic for x = 0.25, 0.50 and 0.75 and Co 2 Fe 0.25 Mn 0.75 Ge is ferrimagnetic. • Maximum spin polarization informs that the studied systems present half-metallic. • Gibbs program and are evaluated as functions of temperature at zero pressure. • Transport coefficients of the considered alloy have been investigated. [ABSTRACT FROM AUTHOR]

Multi-principal element alloys (MPEAs) are promising materials for structural applications under extreme conditions. Their outstanding mechanical properties are closely related to the activation of multiple deformation modes of dislocation gliding, twinning, and phase transformation that appear in sequence during deformation at low temperatures, high pressures, or high strain rates. However, the inherent correlations among these deformation modes and, thus, underlying deformation mechanisms of MPEAs remain largely unknown. We report soft-recovery plate impact experiments of face-centered-cubic (FCC) CrCoNi MPEAs, demonstrating pressure-dependent deformation modes from low-pressure stacking faults to medium-pressure twinning and high-pressure FCC to hexagonal-close-packed (HCP) phase transformation. Atomic-scale characterizations unveil that the sequential deformation is manipulated by the cooperation of 90° and 30° Shockley partial dislocations at deformation fronts, which is facilitated by low stacking fault energy and pressure-dependent phase stability of the MPEAs. Moreover, the cooperative dislocation behavior can also be observed at twin fronts of shock-loaded CrMnFeCoNi MPEA, validating the universality of the cooperative deformation mode in FCC alloys with a low stacking fault energy. Theoretical analyses suggest that the distinctive cooperative dislocation behavior results in the self-compensation of dislocation strain fields and the minimization of interfacial elastic energy at incoherent twin and FCC/HCP interfaces. [Display omitted] [ABSTRACT FROM AUTHOR]

The contradictory relationship between magnetism and ductility restricts further applications of FeCoV alloys in high-performance electrical machines. The role of the BCC-B2 transition, accompanied by vanadium (V) site occupancies, in magnetic moments and ductility has been explored using first-principles calculations. The variations in magnetism and ductility of FeCoV alloys are attributed to the coupling of the BCC-B2 transition and V occupancies. When V replaces Fe atoms in the equiatomic B2-FeCo alloy, the superior magnetism observed in B2-Fe 50- c Co 50 V c alloys is a consequence of the enhanced local magnetic moment of Fe and the ferrimagnetic-ferromagnetic transition in the magnetic state. Moreover, due to the preferential V occupancy in the B2 phase, the B2-Fe 46 Co 50 V 4 alloy exhibits comparable ductility to the BCC-Fe 50 Co 46 V 4 alloy. The results indicate that the increased brittleness in the B2 phase arises from the raised Peierls stress and the enhanced covalent component in interatomic bonding, which is caused by the strong hybridization between Fe and Co atoms. Pearson correlation analysis illustrates that valence electron concentration (VEC) and V content are significant factors in the contradictory relationship between magnetization and ductility. The theoretical results demonstrate that tuning the V content and atomic occupancies is helpful to achieve a trade-off between magnetization and ductility in B2-FeCoV alloys. • The coupling effect of the BCC-B2 transition and V occupations on magnetic moment and ductility. • The underlying origins of magnetism-ductility contradictory relationship. • A trade-off between magnetic moment and ductility can be obtained in B2-Fe 46 Co 50 V 4 alloy. • the magnetization can be improved by adjusting VEC and V content. [ABSTRACT FROM AUTHOR]

• Ti2MnAl crystallizes with significant atomic disorder resulting in random mixing of constituent elements. • Atomic disorder plays an important role in determination of physical properties. • Ti2MnAl exhibits Pauli's paramagnetic behaviour. • Non-interacting superparamagnetic clusters emerge at low temperatures due to defects. • Disorder give rise to a negative temperature coefficient of resistivity. Search for novel spintronic materials in family of Heusler alloys has attained significant interest in recent years. In this context, Ti 2 MnAl is interesting as it is predicted to host spin gapless semiconducting state and compensated ferrimagnetic ordering. Here we report a detailed experimental investigation of Ti 2 MnAl. Our studies reveal that Ti 2 MnAl crystallizes in cubic structure with strong atomic disorder along with Pauli paramagnetic behaviour. The influence of disorder manifests in form of non-interacting superparamagnetic clusters at low temperatures and negative temperature co-efficient of resistivity. The carrier concentration obtained from Hall resistivity rules out the possibility of spin gapless semiconducting state. Our studies indicate that atomic disorder plays an important role in determination of physical properties of Ti 2 MnAl. [ABSTRACT FROM AUTHOR]

Development of antiferromagnetic/ferrimagnetic materials has been an area of active pursuit to advance the antiferromagnetic/ferrimagnetic spintronics. In this paper, we investigated the emergence of the spontaneous magnetization M S in the antiferromagnetic Cr 2 O 3 thin film by the Al substitution. In the case of the (Cr 1- x Al x) 2 O 3 (0001) thin films, M S increases with increasing Al composition x up to x ∼0.21. The magnitude of M S decreases abruptly for x > 0.22, accompanied with the collapse of the crystal formation. We found that the induction of the spontaneous magnetization was highly associated with the growth process. The magnitude of M S depends on the growth direction of the film: M S at 10 K for x = 0.13±0.01 is 80 kA/m, 30 kA/m and 0 kA/m for (0001), (01 1 ¯ 2) and (11 2 ¯ 0) films, respectively. The difference in M S with the growth direction is relevant to the magnetic sublattice selective substitution of Al during the thin film growth. This specific substitution occurs in the growth plane having the layer-by-layer stacking of the magnetic sublattice, which was verified by the direct observations using the scanning transmission electron microscope. [Display omitted] [ABSTRACT FROM AUTHOR]

• Review on recent progress in magnetic properties of SrM magnet & it's applications. • Reviewed various synthesis processes and their effect on magnetic properties of SrM. • Covered substitutional behavior of various elements on magnetic properties of SrM. • Attempted to cover the possibility of SrM-based magnet in numerous applications. • The review paper is motivated towards an alternative to rare-earth permanent magnet. Hard magnets (HMs) are significant components in various applications like rotating machines, telecommunication, computer devices, sensors, and many more. In the HM group, permanent magnets are extensively used due to their high energy product, though they are costly and contain rare earth (RE) elements. Advancements in the magnetic properties of non-RE-based hard magnets can fulfill the technology gap between non-RE and expensive RE-based hard magnets. Hexaferrite magnets represent the largest magnet group being used nowadays by volume, in which strontium hexaferrite (SrM) is a widely used non-RE hard magnet. It is the most faithful base magnet in terms of abundance and economic balance, which requires more or less reformation and advancement in the aspect of magnetic properties. SrMs are ferrimagnetic materials, and their magnetic properties are inherently linked to the microstructures. It can be upgraded to attain high (BH) max and high curie temperature by refining its magnetic properties. Improvement in its M s and H c , even mildly, could open up the possibilities of large-scale immersion of strontium hexaferrite-based magnets in the vast field of permanent magnet applications. In the past several years, enormous improvement has been made toward enhancing the physical and magnetic properties of SrM. Identifying the synthesis parameters as well as the microstructural changes is essential for designing and improvisation of magnets. The current progress in the magnetic properties of SrM (especially high M s and high H c) by synthesis parameters and different substituting elements is briefly covered in this review, along with the applications and future aspects of Sr-hexaferrite-based magnets. [ABSTRACT FROM AUTHOR]

This work used two approaches of mechanical alloying before high temperature solid state reaction to synthesize BaFe 12-x Sc x O 19 (x = 0.5 to 6.0) system. Rietveld refinement of X-ray diffraction patterns showed the formation of extra phases at higher Sc doping, along with the main magnetoplumbite structure. Raman spectroscopy suggested random distribution of Sc ions at the Fe-sites of hexaferrite structure. X-ray photoelectron spectroscopy (XPS) confirmed the +3 charge state at the Fe/Sc-sites. The Fe 3s band suggested dilution of ferromagnetic 3s-3d spin exchange interactions. The neutron diffraction study re-confirmed random occupancy of the non-magnetic Sc3+ ions at Fe3+ sites of the Sc doped Ba hexaferrite system. The transformation of magnetic spin order from collinear to non-collinear state has shown spin glass-like features at low temperature regime in the dc magnetization curves. This is an effect of dilution of Fe– O –Fe ferrimagnetic super exchange interactions and spin frustration in Sc-doped samples. [Display omitted] [ABSTRACT FROM AUTHOR]

Using DFT and Monte Carlo simulation, we studied the physical properties of the ferrimagnetic half-metal Mn 2 RhSi Heusler alloy. Our calculations reveal a stable face-centered cubic structure without any possibility of martensitic transition. The electronic structure shows half-metallic behavior with a band gap in spin-down of 0. 49 eV calculated using PBE and 0. 85 eV using the r 2 SCAN functional, and antiferromagnetic–ferromagnetic coupling with a Curie temperature of 460 K. The elastic constants and moduli decrease with temperature due to thermal expansion, but Mn 2 RhSi retains its mechanical stability. The dominance of metallic bonds, large band gap, high Curie temperature, low magnetic moment, and good mechanical properties make Mn 2 RhSi a promising candidate for spintronic applications at room temperature. • Mn 2 RhSi is an inverse Heusler ferrimagentic half-metal. • According to the r2SCAN functional, Mn 2 RhSi has a spin-down gap of 0.85 eV. • Curie temperature of Mn 2 RhSi calculated using Monte Carlo simulation is 460 K. • Mechanical properties indicate that Mn 2 RhSi is mechanically stable and ductile over the temperature range of 0–1000K. • The wide gap and Curie temperature above room temperature suggest that Mn 2 RhSi can be suitable for spintronic applications. [ABSTRACT FROM AUTHOR]

We used Monte Carlo simulation to study the magnetic properties and compensation behavior of a ferrimagnetic mixed-spin (3 / 2 ; 1 / 2) Ising system in a graphene bilayer. The effects of exchange interactions, crystal field, external magnetic field and temperature on the total magnetization, partial magnetizations, magnetic susceptibility, phase diagram and hysteresis behavior of the system were examined. Interesting results were obtained in this work, such as the compensation behavior and the multi-loop hysteresis phenomenon for specific values of the system's physical parameters. Our results conform to those of other theoretical studies. • The compensation and critical behaviors of a Graphene Bilayer were investigated. • Different total magnetization profiles are observed in this ferrimagnetic system. • The effect of various physical parameters on hysteresis behavior was presented. [ABSTRACT FROM AUTHOR]

The experimental discovery of the suppression effect of the non-collinear phase in strong magnetic fields near the compensation point in ferrimagnetic structures was made. The observations were carried out using the magneto-optical method by creating a lateral temperature gradient in the plane of the epitaxial films of iron garnets. The non-collinear phase is absent in weak magnetic fields. If an external magnetic field exceeds the first critical value, the non-collinear phase arises near the compensation point. The temperature range of the non-collinear phase expands due to the field increase up to the second critical value. Further field increases conversely reduce the temperature range of the non-collinear phase so that the field above the second critical value causes the disappearance of the non-collinear phase. The effect of the occurrence and suppression of the non-collinear phase is demonstrated on samples of two types of iron garnet films with two and three magnetic sublattices. Phase diagrams of the magnetic states in the vicinity of the critical point are constructed, and it is shown that the region of existence of the non-collinear phase in a two-sublattice magnet is smaller than in a three-sublattice one.

CaCu3Fe4O12 exhibits a temperature-induced transition from a ferrimagnetic-insulating phase, in which Fe appears charge disproportionated, as Fe 3 + and Fe 5 + , to a paramagnetic-metallic phase at temperatures above 210 K, with Fe 4 + present. To describe it, we propose a microscopic effective model with two interpenetrating sublattices of Fe ( 4 − δ ) + + and Fe ( 4 + δ ) + + , respectively, δ being a measure of the Fe-charge disproportionation. We include all 3d-Fe orbitals: t 2 g localized orbitals, with spin 3/2 and magnetically coupled, plus two degenerate itinerant eg orbitals with local and nearest-neighbor (NN) electron correlations, and hopping between NN eg orbitals of the same symmetry. Allub and Alascio [J. Phys.: Condens. Matter 24(49), 495601 (2012)] previously proposed a model to describe the phase transition in LaCu3Fe4O12 from a paramagnetic-metal to an antiferromagnetic-insulator, induced by temperature or pressure, involving charge transfer between Fe and Cu ions, in contrast to Fe-charge disproportionation. With the model proposed for CaCu3Fe4O12, modified to account for this difference between the two compounds, the density of states of the itinerant Fe orbitals was obtained, using Green's function methods. The phase diagram of CaCu3Fe4O12 was calculated, including phases exhibiting Fe-charge disproportionation, where the two eg orbitals in each site are symmetrically occupied, as well as novel phases exhibiting local orbital selectivity/asymmetric occupation of eg orbitals. Both kinds of phases may exhibit paramagnetism and ferromagnetism. We determined the model parameters which best describe the phase transition observed in CaCu3Fe4O12 and found other phases in different parameter ranges, which might be relevant for other compounds of the ACu3Fe4O12 family, presenting Fe-charge disproportionation and intersite charge transfer Fe-Cu. [ABSTRACT FROM AUTHOR]

We have demonstrated a ferrimagnetic-type anti-parallel remanent state of rhomboid shaped nanomagnets of two different widths alternated in a dipolar coupled nanomagnetic array. The anti-parallel state is reconfigured to a parallel remanent state by using a simple field initialization process. Magnetic states were directly visualized using the magnetic force microscopy technique. Due to a variation of the stray field distributions for the two different remanent states, distinct dynamic responses are found using the broadband ferromagnetic resonance spectroscopy technique without applying any external bias magnetic field. Experimental observations were supported by the micromagnetic simulations. The results are important in the context of bias-field-free and reprogrammable microwave magnetic devices and creation of artificial ferrimagnetic crystals. [ABSTRACT FROM AUTHOR]