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The magnetic properties of van der Waals materials are profoundly influenced by structural defects. The layered antiferromagnet MnPS3 offers a unique opportunity to explore defect‐related magnetism, as Mn2+ vacancies can be generated by the intercalation of specific guest molecules. However, the effectiveness of this process in atomically thin flakes and the extent of the magnetic tunability remain unclear. Here, it is shown that the magnetic properties of MnPS3 can be tailored through the intercalation of different guest molecules. Notably, the insertion of four alkylammonium ions introduces different populations of Mn2+ vacancies, leading to a transition from the pristine antiferromagnetic state to more complex magnetic textures, including a ferrimagnetic state displaying a magnetic saturation of 1 µB per atom. Moreover, it is shown that the intercalation of few‐nm‐thick flakes also leads to the emergence of a ferrimagnetic response. This in‐flake intercalation, which can be monitored in real time using optical microscopy, can be interrupted before completion, generating lateral heterostructures between pristine and intercalated areas. This approach opens the way to the use of partial intercalation to define regions with distinct magnetic properties within a single flake. [ABSTRACT FROM AUTHOR]

We explored the coupling between magnetic and magneto-transport properties in MnBi2Te4 crystals with Fermi energy EF ranging from 10 to 100 meV in the conduction band. Electrical, magnetic, and magneto-transport measurements reveal distinct behaviors depending on EF. At lower EF values (10 meV), MnBi2Te4 exhibits degenerate-semiconductor-like electrical transport and ferrimagnetism, with weak coupling between magneto-resistance and ferrimagnetism. In contrast, MnBi2Te4 displays metallic transport and antiferromagnetism (AFM) at higher Fermi energies, with magneto-resistance strongly coupled to antiferromagnetism and canted antiferromagnetism under a large external magnetic field. Remarkably, Hall measurements demonstrate a pronounced anomalous Hall resistivity (AHR) when the EF of MnBi2Te4 is 10 meV, larger than that reported for other bulk MnBi2Te4 crystals in the literature. Significant AHR is attributed to the Berry-phase effect in electronic-band structure based on first-principles calculation. The evolution of magnetic and magneto-transport properties in EF shifted MnBi2Te4 can be semi-quantitatively explained by the Ruderman–Kittel–Kasuya–Yosida interaction between neighboring MnTe layers. Our work suggests that the strongly Fermi-energy-sensitive magneto-transport properties observed in MnBi2Te4 may be useful in developing magnetic sensors/detectors. [ABSTRACT FROM AUTHOR]

Siderite is a typical iron-bearing carbonate mineral, which is characterized by thermal instability. In this study, the thermal decomposition of natural siderite with magnesium (Mg) isomorphous substitution was performed in a flowing air atmosphere. During the thermal decomposition, X-ray diffraction, Mössbauer spectroscopy, transmission electron microscope, and vibrating sample magnetometer were employed to characterize the samples. Results indicated that siderite primarily transformed into maghemite and Mg–Fe spinel in oxidation decomposition, and no magnetite was detected. The synthetic spinel phases were highly stable and difficult to oxidize even at a roasting temperature of 700 °C because of the magnesium substitution. Owing to the ferrimagnetism of maghemite and Mg–Fe spinel, the magnetism of samples significantly improved during the oxidation decomposition. [ABSTRACT FROM AUTHOR]

Cubic, perovskite‐structure ABO3‐ and A1−xA'xBO3‐type oxides have been investigated extensively while their hexagonal structure versions have not, even though they are multiferroic and can form heterostructures with hexagonal 2D materials. In particular, multiferroic 2D epilayers may lead to strong magnetoelectric coupling. Hexagonal RFeO3 ferrites, where R is a rare‐earth element (Lu, Yb, etc.), are excellent candidates, but their ferromagnetism is weak. In this work, density‐functional‐theory (DFT) calculations are employed and first show that heavy electron doping of hexagonal LuFeO3 (h‐LFO), namely Lu1−xHfxFeO3 (h‐LHFO), leads to spin‐disproportionation of the Fe sublattices and, especially for x = 1/2 and 2/3, to robust, room‐temperature, out‐of‐plane, collinear ferrimagnetism that is stabilized by a Jahn–Teller metal‐to‐insulator transition. h‐LHFO/h‐2D heterostructures are then shown, where h‐2D is the FE/FM monolayer MnSTe, to stabilize skyrmions without an external magnetic field and their chirality is controlled by an external electric field through the h‐LHFO polarization, opening up a new realm for magnetoelectric applications. [ABSTRACT FROM AUTHOR]

Perpendicularly magnetized Co-based Heusler alloys are promising candidates in high-performance spintronic devices. However, there is a contradiction between thermal stability and damping-like spin–orbit torque (SOT) efficiency in Co-based Heusler alloys with interface-induced perpendicular magnetic anisotropy (PMA). Here, we present epitaxially grown perpendicularly magnetized Mn1+xCo2−xAl (MCA) Heusler alloys through tetragonal distortion. Ferrimagnetism and distortion-induced PMA are obtained in MCA Heusler alloys. A large effective spin Hall angle (θeff) up to 0.33 is experimentally demonstrated in Pt/MCA bilayers, markedly surpassing that in conventional Pt/FM bilayers. Consequently, SOT-induced efficient magnetization switching is realized in Pt/MCA bilayers, with a critical switching current density (Jc) as low as 4 × 107 A/cm2. The large θeff and high SOT efficiency would be attributed to the staggered magnetic exchange torques in the ferrimagnetic MCA Heusler alloys. These findings demonstrate that perpendicularly magnetized ferrimagnetic MCA Heusler alloys are highly promising for high-density SOT-magnetic random-access memory with superior thermal stability and low power consumption. [ABSTRACT FROM AUTHOR]

Nanoscaled magnetic cobalt ferrite (CoFe2O4) of approximately size 17 nm was synthesized via the co-precipitation method and then annealed at 600 °C. The resultant materials were taken for various magnetic characterizations. The X-ray diffraction pattern confirms the formation of the fcc type of cubic crystal structure. The ferrimagnetic phenomenon of the specimen was confirmed by the hysteresis loop, which is comparable to the slow relaxation sextet pattern of the Mӧssbauer study. Isomer shift, quadrupole splitting, hyperfine field, and Fe3+ occupancy of various sites are also investigated from mӧssbauer spectroscopy. The frequency-dependent initial permeability has a comparatively high value up to a certain frequency range and then decreases drastically, whereas the imaginary part of complex permeability decreases sharply with the increase of frequency. The temperature-dependent magnetization ensures the presence of a superparamagnetic blocking temperature of 433 K. In the study of the magnetocaloric effect, isothermal magnetization measurements were carried out around the superparamagnetic blocking temperature, revealing a maximum entropy change of ΔSmax = 1.32 J/kg K and a relative cooling power (RCP) of 52.22 J/kg (H = 1.5 T) through the Maxwell approach. These outcomes emphasize the potential of CoFe2O4 NPs for magnetic refrigeration at reduced temperatures with lower applied magnetic fields.

Present work reports a systematic study on the evaluation of magnetic inhomogeneities in non-stoichiometric Mg 0·5 Ca 0·5 Fe 2 O 4 nanoferrite (MCNF) by conducting exhaustive dc-magnetization, ac-susceptibility and 57Fe Mössbauer spectroscopic measurements and exchange bias investigations using training protocol down to 6 K. Rietveld fitting to PXRD established the formation of anticipated spinel fcc phase of MCNF (non-stoichiometric) along with a minute impurity phase of calcite. Scherrer method and HRTEM micrographs illustrated broad size distribution of MCNF nanoparticles with an average nanocrystallite size of ∼15 nm. Combined 57Fe Mössbauer spectroscopic and dc-magnetization analysis establishes coexistence of ferrimagnetic (67 %) & superparamagnetic (33 %) states at 300 K with notable M s = 22 emu/g, M r = 4 emu/g & H c = 130 Oe and blocking of most of the nanoparticles of MCNF below 300 K. The coercivity followed the size-modified Kneller law for ferrimagnetic nanoparticles and the saturation magnetization abides the Bloch law. Moreover the frequency-dependent ac-susceptibility investigations revealed two magnetic transitions: (i) A transition at ∼ 330 K in the low frequency data attributed to the relaxation of blocked particles of bigger sizes under the superparamagnetic (SPM) regime and (ii) an irregularity at low temperatures is assigned to surface spin glass freezing. Surface spin glass freezing was further affirmed by the ageing experiments and dynamic scaling law. Furthermore, even the best fit to the dynamic scaling couldn't assert the existence of conventional spin glass phase due to slower spin-flip time of surface spins. A soft ferrimagnetic core of MCNF is enveloped with disordered surface spins, which manifest spin glass state. Concurrently, the findings of exchange bias at 30 K and training effect at 6 K affirmed that MCNF nanoparticles are presenting themselves as FM core- SG shell system. Our experimental findings suggested magnetic inhomogeneities comprised of superparamagnetism, ferrimagnetism and disordered surface spin glass state in the non-stoichiometric MCNF. [ABSTRACT FROM AUTHOR]

The preparation of 2D magnetoelectric (ME) nanomaterials with strong ME coupling is crucial for the fast reading and writing processes in the next generation of storage devices. Herein, 2D BaTiO3 (BTO)‐CoFe2O4 (CFO) ME nanocomposites are prepared through a substrate‐free coupling strategy using supercritical CO2. Such 2D BTO‐CFO with strong coupling is built through alternating in‐plane and out‐of‐plane epitaxy stacking, leading to remarkable mutual biaxial strain effects for spin‐lattice coupling. As a results, such strain effect significantly enhances the ferroelectricity of BTO and the ferrimagnetism of CFO, where an unexceptionally high ME coupling coefficient of (325.8 mV cm−1 Oe−1) is obtained for the BTO‐CFO nanocomposites. [ABSTRACT FROM AUTHOR]

We present a study on the structural and magnetic properties of Sr(Fe0.2Mn0.2Co0.2Ti0.2V0.2)O3 (S5BO) high-entropy oxide perovskite thin films. We use synchrotron-based x-ray absorption spectroscopy employing x-ray magnetic circular dichroism (XMCD) and reveal an enhanced presence of high-spin Co2+, which appears to feature a magnetic response opposing that of the two other magnetic transition metal elements, Fe and Mn. This is marked by both opposite XMCD signals and an inverted XMCD hysteresis loop for Co, while Fe and Mn show regularly shaped hysteresis curves, as the picture of a ferrimagnetic ground state emerges for S5BO. [ABSTRACT FROM AUTHOR]

To overcome the challenges related to diluted magnetic semiconductors (DMS), significant research efforts are currently underway to develop functional materials to fulfil the requirements of next-generation spintronic devices. This study was planned to investigate a potential DMS material based on Al2CO using first-principles methods. Al2CO is a direct band gap semiconductor with the energy gap of 1.77 eV in such a way that the conduction band minimum is composed of Al 3 s states, whereas the valence band maximum is contributed by p states of carbon and oxygen atoms. The phonon dispersion curves revealed the dynamical stability of Al2CO. The effect of 3d transition metal (TM) dopants doping into the Al2CO on the electronic and magnetic properties was systematically investigated. The cationic site near oxygen is found energetically feasible when compared with the site adjacent to a carbon atom in the host. The dopants produced spin-polarized gap states in an otherwise non-magnetic host. The hybridization of the p states of the host with the d states of dopant pointing to p-d exchange interactions is observed. The doping of Cr in the host exhibited half-metallic nature of the material. To check the magnetic ground state, double doping with the spin-flip configuration of the host was carried out. The results revealed that the entire 3d dopants prefer to adopt antiferromagnetic coupling in Al2CO. The finding demonstrates that Al2CO is a promising host material for creating new DMS to be used in spintronics. [ABSTRACT FROM AUTHOR]

Magnetic nanomaterials showing unique magnetic behaviour have spread their potential applications in various fields. Iron oxide nanomaterials have been developed for their unique properties that they develop at extremely small size. The high surface area to volume ratio, enhanced surface properties, excellent magnetic property with better biocompatibility are the most promising properties of iron oxide nanoparticles (NPs). Hence development of bio-friendly and less toxic iron oxide NPs is the key point of research in recent years. Most importantly, unique physical and chemical properties of magnetite (Fe3O4), maghemite (γ-Fe2O3) and hematite (α-Fe2O3) are significantly important in the field of technological and biological applications. At nanoscale transition metal iron oxide develops superparamagnetism, which is very important and promising for biomedical applications. In the current study Magnetite (Fe3O4) phase of iron oxide has been prepared in the laboratory using the coprecipitation method. In this study less expensive and widely used experimental setup has been designed to observe the size effect in magnetic iron oxide nanoparticles. The structural information was obtained using X-ray diffraction (XRD). XRD result showed the presence of peaks corresponding to magnetite (Fe3O4) phase of iron oxide. The morphology of the particles was studied using Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Magnetic properties were studied using vibrating sample magnetometer (VSM). Theoretical discussion on superparamagnetism has also been done. [ABSTRACT FROM AUTHOR]

Ce:YIG thin films are taken as an ideal candidate for magneto-optical devices with giant Faraday effect in the near-infrared range, but it is hindered by a limited Ce3+/Ce4+ ratio and a high saturation driving field. To address this issue, Eu doping can increase the Faraday rotation angle by ∼ 40% to 1.315 × 104 deg/cm and decrease the saturation driving field by ∼ 38% to 1.17 kOe in Eu0.75Ce1Y1.25Fe5O12 compared to Ce1Y2Fe5O12 pristine. The mechanism is attributed to the conversion of Ce4+ to Ce3+ and the weakening of ferrimagnetism by Eu doping. This work not only provides strategies for improving Ce3+/Ce4+ ratio in Ce:YIG, but also develops (Eu,Ce):YIG with a promising Faraday rotation angle for magneto-optical devices. [ABSTRACT FROM AUTHOR]

Regulation of electrocatalysis by an external magnetic field has been recently reported, but the physical understanding of what triggers this effect remains elusive. Most cases occur in transition-metal oxychalcogenides with ferromagnetism/ferrimagnetism, but the research on perovskite oxide catalysts is still lacking. In this work, we synthesized a series of Eu element-substituted Ba0.5Sr0.5Co0.8Fe0.2O3 cubic perovskites, and importantly, the regulation of the electrochemical performance by the magnetic field was achieved in Eu0.3(Ba0.5Sr0.5)0.7Co0.8Fe0.2O3 at 273 K, regardless of the direction of the applied magnetic field. Our results promote the use of the magnetic field as an interesting playground to ameliorate electrocatalysis of perovskite oxides close to the paramagnetic state. [ABSTRACT FROM AUTHOR]

Condensed matter physics has often provided a platform for investigating the interplay between particles and fields in cases that have not been observed in high-energy physics. Here, using angle-resolved photoemission spectroscopy, we provide an example of this by visualizing the electronic structure of a noncentrosymmetric magnetic Weyl semimetal candidate NdAlSi in both the paramagnetic and ferrimagnetic states. We observe surface Fermi arcs and bulk Weyl fermion dispersion as well as the emergence of new Weyl fermions in the ferrimagnetic state. Our results establish NdAlSi as a magnetic Weyl semimetal and provide an experimental observation of ferrimagnetic regulation of Weyl fermions in condensed matter. A Weyl semimetal formally requires either broken time reversal symmetry or inversion symmetry. One class of Weyl semimetals-the crystal family of NdAlSi-exhibits both. Here, Li et al perform angle-resolved photoemission spectroscopy measurements on NdAlSi, and observe the formation of an additional Weyl fermion as the material becomes ferrimagnetic. [ABSTRACT FROM AUTHOR]

Using the path probability and lowest approximation of cluster variation method, we study the dynamic and equilibrium properties of a bilayer magnetic system, consisting of two ferromagnetic monolayers antiferromagnetically coupled for different spins (𝜎 = 1/2 and 𝑆 = 1). Firstly, numerical results of the monolayer and total magnetizations are presented under the effect of the diverse physical parameters, and the phase diagrams of bilayer system are discussed. Then, since it is well established that the path probability method is an effective method for the existence of metastable states, the time evolution of monolayer- and total magnetizations is investigated. [ABSTRACT FROM AUTHOR]

Their high tunability of electronic and magnetic properties makes transition‐metal oxides (TMOs) highly intriguing for fundamental studies and promising for a wide range of applications. TMOs with strong ferrimagnetism provide new platforms for tailoring the anomalous Hall effect (AHE) beyond conventional concepts based on ferromagnets, and particularly TMOs with perpendicular magnetic anisotropy (PMA) are of prime importance for today's spintronics. This study reports on transport phenomena and magnetic characteristics of the ferrimagnetic TMO NiCo2O4 (NCO) exhibiting PMA. The entire electrical and magnetic properties of NCO films are strongly correlated with their conductivities governed by the cation valence states. The AHE exhibits an unusual sign reversal resulting from a competition between intrinsic and extrinsic mechanisms depending on the conductivity, which can be tuned by the synthesis conditions independent of the film thickness. Importantly, skew‐scattering is identified as an AHE contribution for the first time in the low‐conductivity regime. Application wise, the robust PMA without thickness limitation constitutes a major advantage compared to conventional PMA materials utilized in today's spintronics. The great potential for applications is exemplified by two proposed novel device designs consisting only of NCO films that open a new route for future spintronics, such as ferrimagnetic high‐density memories. [ABSTRACT FROM AUTHOR]

The structural, magnetic, and dielectric properties of ceramic samples of Yb-doped PbFe2/3W1/3O3 have been investigated by a variety of methods including x-ray powder diffraction, magnetometry, and dielectric spectroscopy. In addition, theoretical investigations were made using first-principles density functional calculations. All the doped samples Pb(Fe1 − xYbx)2/3W1/3O3 (PFYWO) (0.1 ≤ x ≤ 0.5) were found to crystallize in an ordered cubic (F m 3 ¯ m) structure with partial ordering in the B-perovskite sites. Observed changes in the cationic order were accompanied by differences in the dielectric and magnetic responses of the system. While pure PbFe2/3W1/3O3 is antiferromagnetic, the doped Pb(Fe1 − xYbx)2/3W1/3O3 PFYWO samples display excess moments and ferrimagnetic-like behavior, associated with differences in B′ and B″ site occupancies of the magnetic Fe3+ cations. The magnetic transition temperature of the ferrimagnetic phase is found to decrease with increasing Yb content, from TN ∼350 K of the undoped sample down to 137 K for x = 0.5. All PFYWO compounds display a ferroelectric relaxor behavior akin to that of PbFe2/3W1/3O3, albeit our results show significant changes of the frequency and temperature dependence of the dielectric properties. The changes of the properties of PFYWO with increasing Yb substitution can be explained by the changes in the cation size/charge mismatch and the size difference of the two ordered positions. [ABSTRACT FROM AUTHOR]

The magnetic properties of trigonal 3C Fe7S8 nanoparticles, synthesized via the thermal decomposition method, are investigated using temperature-dependent zero-field cooled (ZFC) and field-cooled (FC) magnetization (M–T) curves. The M–T data, recorded at 100 and 1000 Oe, reveal magnetic ordering with high Curie transition temperature (TC > 300 K) in the specimen. The magnetization vs. applied magnetic field (M–H) data measured in the temperature range from 7 to 300 K show that the compound exhibits ferrimagnetic ordering. The values of coercivity (HC), saturation magnetization (M60 kOe) and remanent magnetization (MR) appear to increase at lower measuring temperatures. As the result of increasing M60 kOe at lower measuring temperatures, within the temperature range of 7 to 300 K, the maximum energy product (BHmax) has the highest value of 128 kG Oe at 7 K. [ABSTRACT FROM AUTHOR]

The content of transition‐metal ions and their valence state for three compositions of NixCuyMn3−x−yBO5 are estimated by the methods of X‐ray absorption spectroscopy. In all the three compositions, the copper content does not exceed 0.25. One of the compositions has manganese ions both in the trivalent and bivalent states according to the K‐edge position. The calculations of the total energies of various cation‐ordered structures using the software package Wien2K show that copper ions predominately occupy one site, namely, 2(2d). The measurements of the magnetic properties show two types of magnetic transitions in all the three compositions, with one of them being in the range of 60–75 K and the other one at 10 K. Based on the exchange interactions calculated in the framework of the empirical model, magnetic ordering temperatures are estimated for two‐ and three‐sublattice structures and the magnetic transition in the range of 60–75 K is supposed to be connected with magnetic moment ordering in sites 2 and 3. [ABSTRACT FROM AUTHOR]

The content of transition‐metal ions and their valence state for three compositions of NixCuyMn3−x−yBO5 are estimated by the methods of X‐ray absorption spectroscopy. In all the three compositions, the copper content does not exceed 0.25. One of the compositions has manganese ions both in the trivalent and bivalent states according to the K‐edge position. The calculations of the total energies of various cation‐ordered structures using the software package Wien2K show that copper ions predominately occupy one site, namely, 2(2d). The measurements of the magnetic properties show two types of magnetic transitions in all the three compositions, with one of them being in the range of 60–75 K and the other one at 10 K. Based on the exchange interactions calculated in the framework of the empirical model, magnetic ordering temperatures are estimated for two‐ and three‐sublattice structures and the magnetic transition in the range of 60–75 K is supposed to be connected with magnetic moment ordering in sites 2 and 3. [ABSTRACT FROM AUTHOR]

Ferrimagnetic insulator materials are the enabling technology for the development of next‐generation magnetic devices with low power consumption, high operation speed, and high miniaturization capability. To achieve a high‐density memory device, a combined realization of robust saturation magnetization (Ms), controllable magnetic anisotropy, and high resistivity (ρ) are highly demanded. Despite significant efforts that have been made recently, simultaneously achieving significant enhancements in these properties in a soft magnetic insulator material still remains a great challenge, severely limiting their practical application. Herein, a high‐entropy strategy in an ultra‐thin spinel ferrite (CrMnFeCoNi)3O4 film is reported that exhibits concurrently a superior saturation magnetization (MS = 1198 emu cm−3), low coercivity (HC = 90 Oe), and excellent resistivity (ρ = 1233 Ω cm), as well as switchable magnetic anisotropy. The comprehensive lattice probing and microstructure analysis studies reveal that such desirable ferromagnetic properties originate from the high‐quality structurally ordered but compositionally disordered single‐crystal epitaxial structure. The switchable magnetic anisotropy demonstrated in the high‐entropy ferrite film can be attributed to the new antiferromagnetic rock‐salt phase. This work unveils the critical benefits of the high‐entropy strategy for magnetic oxide thin films, which opens up new opportunities for the development of high‐performance magnetic materials. [ABSTRACT FROM AUTHOR]

The influence of the size of dislocation loops on sublattice ferrimagnetism in graphene is studied. It is shown that graphene and the underlying gold layer with Au/Co dislocation loops of various sizes are characterized by ferrimagnetic ordering within atomic layers. Additional gold adatoms under graphene enhance the induced Rashba spin–orbit coupling in graphene but do not destroy the ferrimagnetic order in graphene. Since gold clusters can remain during the intercalation of gold on the surface of graphene and under graphene, the number and size of clusters after intercalation can be controlled to enhance the induced Rashba interaction and to obtain a topological phase in graphene. [ABSTRACT FROM AUTHOR]

The electrical resistivity, magnetic, and galvanomagnetic properties of the cast and rapid melt quenched Mn3Al Heusler alloy have been studied. Rapid melt quenching was found to result in changing the microstructure of the Mn3Al alloy, which leads to substantial changes in its electronic transport and magnetic properties. It was suggested that for the cast and rapid melt quenched Mn3Al alloy frustrated antiferromagnetic and almost compensated ferrimagnetic state could appear, respectively. It is shown that the preparation and treatment of the Mn3Al compound plays a substantial role in the formation of its electronic and magnetic characteristics. [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]

The appearance of antiferroelectrics (AFE) in the ferrimagnetism (FM) system would give birth to a new type of multiferroic candidate, which is significant to the development of novel devices for energy storage. Here we demonstrate the realization of full antiferroelectrics in a magnetic La0.5Sr0.5Fe12O19 system (AFE+FM), which also presents a strong magnetodielectric response (MD) and magnetoresistance (MR) effect. The antiferroelectric phase was achieved at room temperature by replacing 0.5 Sr2+ ions with 0.5 La2+ ions in the SrFe12O19 compound, whose phase transition temperature of ferroelectrics (FE) to antiferroelectrics was brought down from 174 °C to −141 °C, while the temperature of antiferroelectrics converting to paraelectrics (PE) shifts from 490 °C to 234 °C after the substitution. The fully separated double P-E hysteresis loops reveal the antiferroelectrics in La0.5Sr0.5Fe12O19 ceramics. The magnitude of exerting magnetic field enables us to control the generation of spin current, which induces MD and MR effects. A 1.1T magnetic field induces a large spin current of 15.6 n A in La0.5Sr0.5Fe12O19 ceramics, lifts up dielectric constants by 540%, and lowers the resistance by −89%. The magnetic performance remains as usual. The multiple functions in one single phase allow us to develop novel intelligent devices. [ABSTRACT FROM AUTHOR]

The magnetic superconductors Dy0.8Er0.2Rh3.8Ru0.2B4 (Tc ~ 5.1 K) and Dy0.6Er0.4Rh3.8Ru0.2B4 (Tc ~ 5.8 K) have been prepared by partially substituting Er for Dy in DyRh3.8Ru0.2B4, and their χ(Т), М(B), and (Т) have been studied in detail. The materials have been shown to undergo an antiferromagnetic transition (at ~3 K) similar to that of the magnetic superconductor DyRh3.8Ru0.2B4. Using magnetic moment vs. magnetic field, M(B), measurements for Dy0.8Er0.2Rh3.8Ru0.2B4 and Dy0.6Er0.4Rh3.8Ru0.2B4 samples and the Bean model, we have obtained the critical current density as a function of field, jc(B), and the reduced pinning force as a function of reduced field, Fp(h), for the Er-containing materials. The superconductors with antiferromagnetic order in their magnetic subsystem (Dy0.8Er0.2Rh3.8Ru0.2B4 and Dy0.6Er0.4Rh3.8Ru0.2B4) have been shown to exhibit the largest deviation from the scaling law for h > 0.4. [ABSTRACT FROM AUTHOR]

Structural properties, electronic band profile along with magnetic ordering of the tri-transition quaternary perovskites CaCu3B2Ir2O12 (B = Mn, Fe, Co and Ni) are investigated through generalized gradient approximation plus Hubbard potential (GGA + U) in the framework of density functional theory (DFT). The estimated structural parameters are well consistent with the experiments and it is indicated from formation energy that CaCu3Mn2Ir2O12 is more stable among the series. The optimized magnetic energy curves reveal the spin glass behavior for CaCu3B2Ir2O12 (B = Mn and Fe) and type-I ferrimagnetic order for CaCu3B2Ir2O12 (B = Co and Ni) compounds. The Heisenberg model estimates the J1 (Cu–B), J2 (B–Ir), and J3 (Cu–Ir) interactions that generate the strong long-range interactions through superexchange mechanism. Furthermore, the electronic band profiles reveal that the 3d electrons of Cu and B are localized and responsible for magnetism while the Ir-5d electrons are delocalized and responsible for metallic nature in the compounds. Magnetic susceptibility verifies the estimated results of DFT and Heisenberg model. Due to spin polarization around the Fermi level, low magnetic moments, magnetization, spin glass, and ferrimagnetic nature of these compounds, it is expected that these materials are suitable for spintronic applications. [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]

Nanosheets composed of stacked atomic layers exhibit unique magnetic, electrical, and electrochemical properties. Here, we report the effect of iron substitution on the structure and magnetism of nickel hydroxide, Ni(OH)2, nanosheets. Ni(OH)2 and iron-substituted Ni(OH)2 (5, 10, 20, and 50 atomic % Fe substitution) were synthesized using a rapid microwave-assisted hydrothermal process. Scanning and transmission electron microscopy show the materials are polycrystalline nanosheets that aggregate into micron-sized clusters. From X-ray diffraction characterization, iron substitutes into the α-Ni(OH)2 lattice up to 20 at. % substitution. The nanosheets exhibit different in-plane and through-plane domain sizes, and Fe substitution affects the nanocrystallite shape anisotropy. The magnetic response differs with Fe substitution: 0% and 5% Fe are ferromagnetic, while samples with 10% and 20% Fe are ferrimagnetic. The competing interactions between magnetization sublattices and the magnetic anisotropy due to the crystalline and shape anisotropy of the nanosheets lead to magnetization reversal at low temperatures. The correlation between higher coercivity and larger nanocrystalline size anisotropy with higher Fe % supports that magnetic anisotropy contributes to the observed ferrimagnetism. The interplay of morphology and magnetic response with Fe-substituted Ni(OH)2 nanosheets points to new ways to influence electron interactions in layered materials which has implications for batteries, catalysis, sensors, and electronics. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) magnetic materials promise unconventional properties and quantum phases as well as advances in ultra-compact spintronics. Miniaturization of 2D magnets often reaches a single monolayer but in general can go beyond this limit, as demonstrated by 2D magnetism of submonolayer Eu superstructures coupled with Si. The question is whether the submonolayer magnetism constitutes a general phenomenon. Herein, we demonstrate that regular Eu lattices form a class of 2D magnets displaying various structures, stoichiometries, and chemical bonding. We synthesized and studied a set of Eu superstructures on Ge(001). Their magnetic properties are consistent with the emergence of a magnetic order such as ferro- or ferrimagnetism. In particular, control over the magnetic transition temperature by weak magnetic fields indicates the 2D nature of the magnetism. Taken together, Eu/Ge and Eu/Si superstructures seed a nucleus of the research area addressing the emergence of magnetism in submonolayer chemical species. [ABSTRACT FROM AUTHOR]

Using the path probability and lowest approximation of cluster variation method, we study the dynamic and equilibrium properties of a bilayer magnetic system, consisting of two ferromagnetic monolayers antiferromagnetically coupled for different spins (σ = 1/2 and S = 1). Firstly, numerical results of the monolayer and total magnetizations are presented under the effect of the diverse physical parameters, and the phase diagrams of bilayer system are discussed. Then, since it is well established that the path probability method is an effective method for the existence of metastable states, the time evolution of monolayer- and total magnetizations is investigated.

Ferrimagnets are of interest in spintronics owing to the enhancement of spin transfer and spin–orbit torque in the vicinity of the magnetic compensation point. Here, we study the possibility of achieving compensation at room temperature in Mn4−xNixN films grown on SrTiO3(001) substrates by molecular beam epitaxy. The magnetic and magneto-transport properties of 30-nm-thick epitaxial Mn4−xNixN films (x = 0, 0.1, 0.25, and 0.5) were investigated. Ni introduction in Mn4N causes the spontaneous magnetization (MS) to decrease by 45% at x = 0.1 and by 75% at x = 0.25. All samples exhibited the perpendicular magnetic anisotropy required for spintronic applications as well as displaying a sharp magnetization reversal. Remarkably, the sign of the anomalous Hall resistivity changed in the samples between x = 0.1 and 0.25. Further, the magnetization increased for x = 0 and 0.1 and decreased for x = 0.25 when the temperature was decreased. Based on these results, we propose that there is a magnetic compensation composition between x = 0.1 and 0.25, where the magnetization of Mn4−xNixN becomes zero at room temperature. The small MS and perpendicular magnetic anisotropy of the Mn4−xNixN thin films, thus, make them suitable candidates for use in spin transfer torque-based devices. [ABSTRACT FROM AUTHOR]

We have investigated the structural, magnetic, and thermal transport properties of Co 1 − x Ni x Cr 2 O 4 (0 ≤ x ≤ 1) to check the evolution of structural and magnetic properties upon the introduction of the Jahn–Teller active ion Ni 2 + . The x ≤ 0.95 samples can be indexed with a cubic lattice with the space group Fd3m, whereas the x = 0.98 sample undergoes a cubic-tetragonal structural transition, and the x > 0.98 samples belong to a tetragonal lattice with the space group I41-amd at room temperature. All these samples undergo a paramagnetic–ferrimagnetic transition at T C. A spiral ferrimagnetic ordering at T S is suppressed when the amount of Ni is increased, and the abnormal magnetization at T S for the x = 0.6 and 0.8 samples is not pronounced. The measurements of magnetic hysteresis reveal that the x = 0.4 and 0.6 samples possess a rather large coercivity H C compared with the x = 0 and 1 samples. Specifically, the x = 0.4 and 0.6 samples undergo a short-range antiferromagnetic transition above T C. The magnetic properties of the Ni-doped samples can be understood in terms of the magnetic structure model consisting of longitudinal and transverse magnetic sublattices. [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]

Defect-induced magnetic phases of 2D and 3D MnB were discussed. The exciting ferromagnetic behavior of MnB MBene is particularly tracked, including high-rated Mn defects via ab-initio calculations and Monte Carlo simulations. Ground state solution was achieved through GGA in PBESol scheme resulting in magnetic state and moments of Mn ions including the density of states around Fermi level. Magnetic susceptibility and magnetization behavior related to temperature was obtained through Monte Carlo simulations based on the Heisenberg model applying Metropolis criteria. The authors focused on controlling the Curie temperature considering the location of Mn defects. The coexistence of the various defect locations opened a realistic window to estimate Curie temperature consistent with experimental values. Exchange energies of 2D MnB different defect locations quite differ from each other. In addition, magnetic moments of the sheet material were found to be higher than 3D bulk MnB.

Ultrafast laser-induced dynamics in a ferrimagnetic gadolinium iron cobalt (Gd/FeCo) multilayer with a magnetization compensation temperature of TM = 320 K is studied at room temperature as a function of laser-fluence and strength of the applied magnetic field. The dynamics is found to be substantially different from that in archetypical GdFeCo alloys, and depending on the laser fluence one can distinguish two different regimes. At low laser fluence (≤1.6 mJ cm-2), ultrafast laser excitation of the medium triggers spin precession of an extraordinary large amplitude reaching over 30°. At high laser fluence (≥2.2 mJ cm-2), the pump heats the medium over the magnetization compensation point, spin precession reduces significantly in amplitude and the process of field-assisted reversal of magnetization of Gd and FeCo is launched. It is argued that such a distinctly different laser-induced magnetization dynamics in the multilayers compared to the alloys is due to the symmetry breaking at the numerous interfaces, giving rise to additional surface anisotropy. The temperature dependence of the latter is found to be the key ingredient in the mechanism of ultrafast laser-induced magnetization dynamics in ferrimagnetic multilayers. Controlling the amount and properties of interfaces in multilayers can thus serve as a mean to achieve efficient ultrafast all-optical control of magnetism. [ABSTRACT FROM AUTHOR]

The magnetic and magnetic entropy behaviors of the CaBaCo4O7 with Al-doping CaBaCo3.96Al0.06O7 and Ni-doping CaBaCo3.96Ni0.06O7 compound are observed. When compared with the Al-doping, Ni-doping shows that a huge decrease of ferrimagnetism is produced. For Al-doping, the magnetic measurements suggest that spin-glass and ferromagnetic transitions are observed at 25 K and 45 K. For Ni-doping, besides the above two transitions, another peak is observed due to the antiferromagnetic (AFM) phase appearance at ~ 80 K. The plot of H/M vs M2 of the isotherms in the vicinity of the Curie temperature suggests that this phase transition was first-order phase transition for all compounds. With decreasing the temperature, the system enters charge-order state and the negative entropy is observed for CaBaCo4O7 and CaBaCo3.96Al0.04O7 compound. However, unlike the nonmagnetic doping, replacement of Co2+ in the zig-zag ferromagnetic chain by Ni2+ does not truncate the chain, but it perturbs the magnetic interaction through antiferromagnetic exchange with cobalt following Goodenough–Kanamori rules. This possibly reorients the cobalt spins adjacent to the dopant in the chain which modifies ferrimagnetic ground state resulting in competing magnetic states. These are likely responsible for the change in magnetic ground state of CaBaCo4O7, this results in suppression of ferrimagnetic state with the evolution of antiferromagnetism and magnetic frustration. The result suggests that the AFM interaction between the dopant Ni2+ and Co2+ ions has a crucial role in the destabilization of the ferromagnetic structure, whereas the triangular geometry of the cobalt sublattice imposes the appearance of magnetic frustration. [ABSTRACT FROM AUTHOR]

We present an exploration of a family of compositionally complex cubic spinel ferrites featuring combinations of Mg, Fe, Co, Ni, Cu, Mn, and Zn cations, systematically investigating the average and local atomic structures, chemical short-range order, magnetic spin configurations, and magnetic properties. All compositions result in ferrimagnetic average structures with extremely similar local bonding environments; however, the samples display varying degrees of cation inversion and, therefore, differing apparent bulk magnetization. Additionally, first-order reversal curve analysis of the magnetic reversal behavior indicates varying degrees of magnetic ordering and interactions, including potentially local frustration. Finally, reverse Monte Carlo modeling of the spin orientation demonstrates a relationship between the degree of cation inversion and the spin collinearity. Collectively, these observations correlate with differences in synthesis procedures. This work provides a framework for understanding magnetic behavior reported for "high-entropy spinels," revealing many are likely compositionally complex oxides with differing degrees of chemical short-range order—not meeting the community established criteria for high or medium entropy compounds. Moreover, this work highlights the importance of reporting complete sample processing histories and investigating local to long-range atomic arrangements when evaluating potential entropic mixing effects and assumed property correlations in high entropy materials. [ABSTRACT FROM AUTHOR]

Using the microscopic three temperature model, we simulate single-pulse all-optical switching (AOS) in alloys and bilayers consisting of Co and Gd. In particular, we investigate its dependence on the spin-flip probability of Gd a sf,Gd , a material parameter describing the strength of spin-phonon coupling. We do so to elucidate the mechanisms behind all-optical switching in systems where Co is coupled to heavy rare-earth elements with higher damping such as Tb. In alloys, our observations are twofold. First, an increase of a sf,Gd leads to a broadening of the range of compositions for which AOS is observed. Second, the ideal Co content is decreased as a sf,Gd is varied. For bilayers, our analysis indicates that switching is most efficient when a sf,Gd takes on small values. Conversely, increasing the value of a sf,Gd leads to a general suppression of AOS. Comparing alloys to bilayers, we find that AOS in alloys exhibits greater resilience to variations in a sf,Gd than it does in bilayers. • Increasing a sf,Gd alters ideal conditions for all-optical switching (AOS) in alloys. • In bilayers, increasing a sf,Gd results in a gradual suppression of AOS for thick Co layers. • Alloys are more resilient than bilayers against variations in a sf,Gd. • M3TM simulations are in qualitative agreement with atomistic simulations and experiments. [ABSTRACT FROM AUTHOR]

Inversion symmetry breaking has become a vital research area in modern magnetism with phenomena including the Rashba effect, spin Hall effect, and the Dzyaloshinskii-Moriya interaction (DMI)-a vector spin exchange. The latter one may stabilize chiral spin textures with topologically nontrivial properties, such as Skyrmions. So far, chiral spin textures have mainly been studied in helimagnets and thin ferromagnets with heavy-element capping. Here, the concept of chirality driven by interfacial DMI is generalized to complex multicomponent systems and demonstrated on the example of chiral ferrimagnetism in amorphous GdCo films. Utilizing Lorentz microscopy and X-ray magnetic circular dichroism spectroscopy, and tailoring thickness, capping, and rare-earth composition, reveal that 2 nm thick GdCo films preserve ferrimagnetism and stabilize chiral domain walls. The type of chiral domain walls depends on the rare-earth composition/saturation magnetization, enabling a possible temperature control of the intrinsic properties of ferrimagnetic domain walls.

Powders of the system (1–x)Bi0.5Na0.5TiO3–xBiFeO3 (x = 0, 0.02, 0.08, 0.10) are synthesized by the combustion reaction method. The crystal structure and the particle size of Bi0.5Na0.5TiO3 are modified by the incorporation of BiFeO3, as can be seen from the infrared spectroscopy and X-ray diffraction results. The inclusion of iron and the increase in the molar percentage of bismuth in the BNT matrix generate new bonds with a different force constant. The structural analysis showed that the addition of BFO to the BNT does not induce any structural phase transition, preserving the rhombohedral symmetry of the Bi0.5Na0.5TiO3 system. The electrical measurements show that the incorporation of iron increases the conductivity of the system generated by an increase in the concentration of oxygen vacancies; alternatively, the addition of 10% of BiFeO3 generates ferrimagnetic behavior reflected in the magnetic hysteresis curves obtained at room temperature.

Abstract Ultrafast laser‐induced dynamics in a ferrimagnetic gadolinium iron cobalt (Gd/FeCo) multilayer with a magnetization compensation temperature of TM = 320 K is studied at room temperature as a function of laser‐fluence and strength of the applied magnetic field. The dynamics is found to be substantially different from that in archetypical GdFeCo alloys, and depending on the laser fluence one can distinguish two different regimes. At low laser fluence (⩽1.6 mJ cm‐2), ultrafast laser excitation of the medium triggers spin precession of an extraordinary large amplitude reaching over 30°. At high laser fluence (⩾2.2 mJ cm‐2), the pump heats the medium over the magnetization compensation point, spin precession reduces significantly in amplitude and the process of field‐assisted reversal of magnetization of Gd and FeCo is launched. It is argued that such a distinctly different laser‐induced magnetization dynamics in the multilayers compared to the alloys is due to the symmetry breaking at the numerous interfaces, giving rise to additional surface anisotropy. The temperature dependence of the latter is found to be the key ingredient in the mechanism of ultrafast laser‐induced magnetization dynamics in ferrimagnetic multilayers. Controlling the amount and properties of interfaces in multilayers can thus serve as a mean to achieve efficient ultrafast all‐optical control of magnetism.

Single phase materials showing large Exchange Bias (EB) at elevated temperatures are highly desirable for their technological advantage. However, the fundamental interactions leading to the effect are often very complex and ill-understood. Here, we report the observation of EB in single phase (111) oriented MgFe2O4(MFO) thin films on MgO buffered Si(100). The effect is seen to persist till a significantly higher temperature of 110 K. Measurements on stoichiometric powder MFO showed the absence of EB, lower coercivity, and an enhanced saturation magnetization in comparison to thin films. This suggests the modified exchange interaction in the thin films possibly due to the presence of growth induced magnetic and structural disorder. Investigation on the nature of this EB produced some results which are akin to a conventional FM/AFM coupled system like the training effect. However, the same could not explain the observed variation in coercivity and the exchange bias field with temperature and cooling fields. We propose the existence of a disordered layer with random spin orientations at the crystalline grain boundaries of our film, promoting the AFM interaction between the ordered ferrimagnetic grains once field cooled below the spin freezing temperature. This generates a unidirectional anisotropy along the field direction which manifests as a loop shift in hysteresis measurements. A further study shows that the EB field can be varied systematically by changing the thickness of the thin films. This indicates a simple way to tune the disorder for achieving desirable magnetic properties in single phase magnetic thin films. [ABSTRACT FROM AUTHOR]

The influence of epitaxial strain on the electronic, magnetic, and optical properties of the distorted double perovskite Ca2FeOsO6 is studied. These calculations show that the compound realizes a monoclinic structure with P21/n space group from −6% to +6% strain. While it retains ferrimagnetic ordering with a net magnetic moment of 2 μB per formula unit at low strain, it undergoes transitions into E‐antiferromagnetic and C‐antiferromagnetic phases at −5% and +5% strain, respectively. It is shown that spin frustration reduces the critical temperature of the ferrimagnetic ordering from the mean field value of 600–350 K, in excellent agreement with the experimental value of 320 K. It is also shown that the critical temperature can be tuned efficiently through strain and that the spin coherence length surpasses that of Sr2FeMoO6 under tensile strain. An indirect‐to‐direct bandgap transition is observed at +5% strain. Localization of the valence and conduction states on different transition metal sublattices enables efficient electron–hole separation upon photoexcitation. The calculated spectroscopic limited maximum efficiency of up to 33% points to excellent potential of Ca2FeOsO6 in solar cell applications. [ABSTRACT FROM AUTHOR]

Using combined synthesis modes and optimized conditions for ultrasonic dispersion, we obtained a single-phase nanosized Sr 2 FeMoO 6–δ powder having a high degree of superstructural ordering of Fe and Mo cations (88 %) and an average grain size of 70.8 nm. The results of the Mössbauer spectroscopy and magnetic measurements show that the obtained nanosized strontium ferromolybdate powder is in a magnetically inhomogeneous state, consisting of superparamagnetic and ferrimagnetic phases. In comparison with the superparamagnetic component of magnetization, the ferrimagnetic component has higher values and rises smoothly until reaching saturation as the temperature decreases. Showing that there is no exchange magnetic interaction between the grains in the superparamagnetic phase, allowed us to estimate the critical sizes, of nanoparticles, d spm , in the single-domain state using the Néel-Brown model. The obtained value of d spm is smaller than the size of the single-domain particles, which confirms the absence of the frozen state in some of the superparamagnetic particles. These results are important for understanding the effects of nanosized grains on the magnetic properties and features of magnetization of the Sr 2 FeMoO 6–δ polydisperse powder, a promising material for spintronic device applications. [ABSTRACT FROM AUTHOR]