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Antiferromagnetic van der Waals‐type M2P2X6 compounds provide a versatile material platform for studying 2D magnetism and relevant phenomena. Establishing ferromagnetism in 2D materials is technologically valuable. Though magnetism is generally tunable via a chemical way, it is challenging to induce ferromagnetism with isovalent chalcogen and bimetallic substitutions in M2P2X6. Here, we report co‐substitution of Cu1+ and Cr3+ for Ni2+ in Ni2P2S6, creating CuxNi2(1‐x)CrxP2S6 medium‐entropy alloys spanning a full substitution range (x = 0 to 1). Such substitution strategy leads to a unique evolution in crystal structure and magnetic phases that are distinct from traditional isovalent bimetallic doping, with Cu and Cr co‐substitution enhancing ferromagnetic correlations and generating a weak ferromagnetic phase in intermediate compositions. This aliovalent substitution strategy offers a universal approach for tuning layered magnetism in antiferromagnetic systems, which along with the potential for light‐matter interaction and high‐temperature ferroelectricity, can enable multifunctional device applications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) layered materials have been studied in depth during the past two decades due to their unique structure and properties. Transition metal (TM) intercalation of layered materials have been proven as an effective way to introduce new physical properties, such as tunable 2D magnetism, but the direct growth of atomically thin heteroatoms-intercalated layered materials remains untapped. Herein, we directly synthesize various ultrathin heteroatoms-intercalated 2D layered materials (UHI-2DMs) through flux-assisted growth (FAG) approach. Eight UHI-2DMs (V1/3NbS2, Cr1/3NbS2, Mn1/3NbS2, Fe1/3NbS2, Co1/3NbS2, Co1/3NbSe2, Fe1/3TaS2, Fe1/4TaS2) were successfully synthesized. Their thickness can be reduced to the thinnest limit (bilayer 2D material with monolayer intercalated TM), and magnetic ordering can be induced in the synthesized structures. Interestingly, due to the possible anisotropy-stabilized long-range ferromagnetism in Fe1/3TaS2 with weak interlayer coupling, the layer-independent magnetic ordering temperature of Fe1/3TaS2 was revealed by magneto-transport properties. This work establishes a general method for direct synthesis of heteroatom-intercalated ultrathin 2D materials with tunable chemical and physical properties. The intercalation of heteroatoms has been demonstrated to be an effective approach to introduce new physical properties in 2D layered materials (2DMs). Here, the authors report a flux-assisted growth method to synthesize various ultrathin heteroatoms-intercalated 2DMs, showing evidence of anisotropy-stabilized long-range ferromagnetism in Fe1/3TaS2. [ABSTRACT FROM AUTHOR]

Cobalt telluride, with tunable magnetism and ferromagnetism that hinged upon the stoichiometric ratio, has emerged as a new member of 2D materials in the last decade. Metallic doping by sodium (Na) and platinum (Pt) atoms below critical concentrations is found to enhance the magnetism of cobalt telluride. After thinning cobalt telluride down to few‐layer, the saturation magnetism is improved by two order of magnitudes because of the oxidation state of cobalt (Co) and reduced coordination number of the surface atoms. In 2D limit, cobalt di‐telluride possesses Dirac band structure with many nodal lines that correlate with quantum criticality and other fantastic physics. In this mini‐review, the crystal and band structures of cobalt telluride categorized by stoichiometric ratio are overviewed after briefing the introduction. Both top‐down and bottom‐up methods are then discussed to offer optimum solutions for each specified application scenario. Afterward, emerging magnetic and electronic properties and credit enhancements are launched accompanied with their key advances. Beyond these, the faced challenges and possible directions of future research are also provided, attempting to boost both fundamental physics and device applications based on 2D cobalt telluride. [ABSTRACT FROM AUTHOR]

We develop a strong coupling approach towards quantum magnetism in Mott insulators for Wannier-obstructed bands. Despite the lack of Wannier orbitals, electrons can still singly occupy a set of exponentially localized but nonorthogonal orbitals to minimize the repulsive interaction energy. We develop a systematic method to establish an effective spin model from the electron Hamiltonian using a diagrammatic approach. The nonorthogonality of the Mott basis gives rise to multiple new channels of spin-exchange (or permutation) interactions beyond Hartree–Fock and superexchange terms. We apply this approach to a Kagome lattice model of interacting electrons in Wannier-obstructed bands (including both Chern bands and fragile topological bands). Due to the orbital nonorthogonality, as parameterized by the nearest-neighbor orbital overlap g, this model exhibits stable ferromagnetism up to a finite bandwidth W ∼ U g , where U is the interaction strength. This provides an explanation for the experimentally observed robust ferromagnetism in Wannier-obstructed bands. The effective spin model constructed through our approach also opens up the possibility for frustrated quantum magnetism around the ferromagnet-antiferromagnet crossover in Wannier-obstructed bands. [ABSTRACT FROM AUTHOR]

Primary ferroicities like ferroelectricity and ferromagnetism are essential physical properties of matter. Multiferroics, with coexisting multiple ferroic orders in a single phase, provide a convenient route to magnetoelectricity. Even so, the general tradeoff between magnetism and polarity remains inevitable, which prevents practicable magnetoelectric cross-control in the multiferroic framework. Here, an alternative strategy, i.e., the so-called alterferroicity, is proposed to circumvent the magnetoelectric exclusiveness, which exhibits multiple but noncoexisting ferroic orders. The natural exclusion between magnetism and polarity, as an insurmountable weakness of multiferroicity, becomes a distinct advantage in alterferroicity, making it an inborn rich ore for intrinsic strong magnetoelectricity. The general design rules for alterferroic materials rely on the competition between the instabilities of phononic and electronic structures in covalent systems. Based on primary density functional theory calculations, Ti-based trichalcogenides are predicted to be alterferroic candidates, which exhibit unique seesaw-type magnetoelectricity. This alterferroicity, as an emerging branch of the ferroic family, reshapes the framework of magnetoelectricity, going beyond the established scenario based on multiferroicity. [ABSTRACT FROM AUTHOR]

The area of intrinsic two-dimensional (2D) materials is spreading widely day by day due to their easily availability and interesting applications. As a newly exfoliated 2D material from bulk Cr2O3 mineral, 2D-Chromia is most far ultrathin magnetic indirect band gap semiconductor with low Curie Temperature (TC). For the present work, we have carried out the detailed structural analysis of 2D-Chromia by prefacing strain via means of density functional theory (DFT). 2D-Chromia in pristine form comes out to ferromagnetic with considerable total spin magnetic moment of 12 μB per unit cell and large band gap (0.72/3.71 eV in majority/minority spin channel). But the presence of low TC and large band gap limits its applications. Thus, in present work, we have checked the dependence of magnetic state and band gap on tensile and compressive strains. Our results indicate that band gap depends strongly on both the strains but magnetic ground state remains unaffected on applying strain. These findings summarize that the resulting 2D-Chromia under study has broad application prospective in spintronics, transistors, and memory-based devices. [ABSTRACT FROM AUTHOR]

2D ferromagnetic semiconductors are key to next‐generation spintronic devices in the post‐Moore era. The combination of ferromagnetic and optoelectronic properties offers exciting opportunities for advanced multifunctional devices in spin‐optoelectronic applications. Herein, the authors synthesize 2D van der Waals (vdW) CoxSn1‐xS with ferromagnetism and photoresponse through a bottom‐up reaction, which has a high yield compared to typical mechanical exfoliation. Ferromagnetic ordering is realized in 2D vdW semiconductor SnS by Co doping at the Sn sites. Magnetic properties are thoroughly studied at different doping concentrations, and first‐principles calculations are further performed to reveal the magnetism origin and spin interactions. In particular, a low Gilbert damping of 1.69 × 10−3 is obtained in vdW CoxSn1−xS through ferromagnetic resonance. In addition, photodetectors based on CoxSn1−xS quantum dots are demonstrated. These studies establish a promising semiconductor with both ferromagnetic ordering and photoelectric response, which provides unprecedented opportunities in spintronic‐photonic integrated applications. [ABSTRACT FROM AUTHOR]

2D half‐metallic materials that have sparked intense interest in advanced spintronic applications are essential to the developing next‐generation nanospintronic devices. This study has adopted a first‐principles calculation method to predict the magnetic properties of intrinsic, Se‐doped, and biaxial strain tuning Cr2AsP monolayer. The Janus Cr2AsP monolayer is proven to be an intrinsic ferromagnetic (FM) semiconductor with an exchange splitting bandgap of 0.15 eV at the PBE+U level. Concentration‐dependent Se doping, such as Cr2As1−x$_{1-x}$SexP (x = 0.25, 0.50, 0.75), can regulate Cr2AsP from FM semiconductor to FM half‐metallicity. Specifically, the spin‐up channel crosses the Fermi level, while the spin‐down channel has a bandgap. More interestingly, the wide half‐metallic bandgaps and spin bandgaps make them have important implications for the preparation of spintronic devices. At last, it also explore the effect of biaxial strain from ‐14% to 10% on the magnetism of the Cr2AsP monolayer. There appears a transition from FM to antiferromagnetic (AFM) at a compressive strain of ‐10.7%, originating from the competition between the indirect FM superexchange interaction and the direct AFM interaction between the nearest neighboring Cr atoms. Additionally, when the compressive strain is ‐2% or the tensile strain is 6%, the semiconducting Cr2AsP becomes a half‐metallic material. These charming properties render the Janus Cr2AsP monolayer with great potential for applications in spintronic devices. [ABSTRACT FROM AUTHOR]

The field of two-dimensional (2D) ferromagnetism has been proliferating over the past few years, with ongoing interests in basic science and potential applications in spintronic technology. However, a high-resolution spectroscopic study of the 2D ferromagnet is still lacking due to the small size and air sensitivity of the exfoliated nanoflakes. Here, we report a thickness-dependent ferromagnetism in epitaxially grown Cr2Te3 thin films and investigate the evolution of the underlying electronic structure by synergistic angle-resolved photoemission spectroscopy, scanning tunneling microscopy, x-ray absorption spectroscopy, and first-principle calculations. A conspicuous ferromagnetic transition from Stoner to Heisenberg-type is directly observed in the atomically thin limit, indicating that dimensionality is a powerful tuning knob to manipulate the novel properties of 2D magnetism. Monolayer Cr2Te3 retains robust ferromagnetism, but with a suppressed Curie temperature, due to the drastic drop in the density of states near the Fermi level. Our results establish atomically thin Cr2Te3 as an excellent platform to explore the dual nature of localized and itinerant ferromagnetism in 2D magnets. Over the last few years, several van der Waals materials have been found that retain magnetic ordering down to monolayer thickness. These materials provide a simple platform for studying the magnetism in reduced dimensions. Here, Zhong et al study the thickness dependence of magnetic ordering in Cr2Te3, and find a crossover from Stoner to Heisenberg-type magnetism as thicknesses are reduced. [ABSTRACT FROM AUTHOR]

The magnetic properties of layered nanowires (NWs) composed of alternating nickel and copper layers were studied. In such structures, magnetic properties are governed by several factors, such as the aspect ratio of alternating layers, the dipole interaction between neighboring layers within a single NW, and the interaction of neighboring NWs. NW arrays were formed by matrix synthesis. Nickel layers had a fixed thickness of 400 nm, and the thickness of copper layers varied from 25 to 300 nm. The magnetic characteristics of such NWs were studied in two states: in a matrix (integral magnetic characteristics determined by vibrating sample magnetometry) and for individual NWs (local magnetization visualized by magnetic force microscopy (MFM)). For NWs in a matrix, the hysteresis loops measured for two magnetic field directions became identical when the thickness of a Cu layer increased to 300 nm due to the weakening of dipole interaction between Ni layers inside NWs and the growing role of dipole interaction between neighboring NWs. In this case, the residual magnetization grew after a field parallel to the matrix plane was applied. The samples with a Cu layer thickness of 300 nm were studied by MFM. It was step-by-step demonstrated how the application of an external magnetic field led to magnetization reversal. Magnetization reversal in a pair of NWs was revealed to occur in two stages like in a two-phase system with two characteristic fields: Hc1 = 40–50 Oe for the formation of a pair with the opposite magnetization direction and Hc2 =160 Oe for complete magnetization reversal. The latter value was close to the coercive force for an array of NWs in a matrix. [ABSTRACT FROM AUTHOR]

Two-dimensional van der Waals materials have attracted considerable attention because of their promising applications in spintronic devices. This paper reports on first-principles calculations of the electronic structure and ferromagnetism of Cr 2 Ge 2 Te 6 with surface Ge vacancies. These vacancies are found to remove the bandgap and induce metallicity in Cr 2 Ge 2 Te 6 that persists with decreasing Ge-vacancy concentration. Meanwhile, the Ge vacancies cause an unexpected sharp increase in the magnetic anisotropy energy compared to that of perfect Cr 2 Ge 2 Te 6. More importantly, how thickness affects the magnetic anisotropy energy is studied to show that the latter oscillates upon increasing the number of layers, thereby switching between the out-of-plane and in-plane magnetization directions. The present findings regarding a surface-vacancy-tuned bandgap and magnetism controlled by the layer thickness in a two-dimensional van der Waals magnet could lead to potential applications in next-generation magnetic memory storage, sensors, and spintronics. [ABSTRACT FROM AUTHOR]

Two-dimensional van der Waals materials have attracted considerable attention because of their promising applications in spintronic devices. This paper reports on first-principles calculations of the electronic structure and ferromagnetism of Cr 2 Ge 2 Te 6 with surface Ge vacancies. These vacancies are found to remove the bandgap and induce metallicity in Cr 2 Ge 2 Te 6 that persists with decreasing Ge-vacancy concentration. Meanwhile, the Ge vacancies cause an unexpected sharp increase in the magnetic anisotropy energy compared to that of perfect Cr 2 Ge 2 Te 6. More importantly, how thickness affects the magnetic anisotropy energy is studied to show that the latter oscillates upon increasing the number of layers, thereby switching between the out-of-plane and in-plane magnetization directions. The present findings regarding a surface-vacancy-tuned bandgap and magnetism controlled by the layer thickness in a two-dimensional van der Waals magnet could lead to potential applications in next-generation magnetic memory storage, sensors, and spintronics. [ABSTRACT FROM AUTHOR]

Micromagnetic simulations are a valuable tool to increase our understanding of nanomagnetic systems and to guide experiments through parameter spaces that would otherwise be difficult and expensive to navigate. To fulfill this task, simulations have always pushed the limits of what is possible in terms of software and hardware. In this perspective, we give an overview of the current state of the art in micromagnetic simulations of ferromagnetic materials followed by our opinion of what tomorrow's simulations will look like. Recently, the focus has shifted away from exclusively trying to achieve faster simulations, toward extending pure micromagnetic calculations to a multiphysics approach. We present an analysis of how the performance of the simulations is affected by the simulation details and hardware specifications (specific to the graphics processing unit-accelerated micromagnetic software package mumax 3), which sheds light on how micromagnetic simulations can maximally exploit the available computational power. Finally, we discuss how micromagnetic simulations can benefit from new hardware paradigms like graphics cards aimed at machine learning. [ABSTRACT FROM AUTHOR]

The recent realizations of the quantum anomalous Hall effect (QAHE) in MnBi2Te4 and MnBi4Te7 benchmark the (MnBi2Te4)(Bi2Te3)n family as a promising hotbed for further QAHE improvements. The family owes its potential to its ferromagnetically (FM) ordered MnBi2Te4 septuple layers (SLs). However, the QAHE realization is complicated in MnBi2Te4 and MnBi4Te7 due to the substantial antiferromagnetic (AFM) coupling between the SLs. An FM state, advantageous for the QAHE, can be stabilized by interlacing the SLs with an increasing number n of Bi2Te3 quintuple layers (QLs). However, the mechanisms driving the FM state and the number of necessary QLs are not understood, and the surface magnetism remains obscure. Here, robust FM properties in MnBi6Te10 (n = 2) with Tc ≈ 12 K are demonstrated and their origin is established in the Mn/Bi intermixing phenomenon by a combined experimental and theoretical study. The measurements reveal a magnetically intact surface with a large magnetic moment, and with FM properties similar to the bulk. This investigation thus consolidates the MnBi6Te10 system as perspective for the QAHE at elevated temperatures. [ABSTRACT FROM AUTHOR]

The recent realizations of the quantum anomalous Hall effect (QAHE) in MnBi2Te4 and MnBi4Te7 benchmark the (MnBi2Te4)(Bi2Te3)n family as a promising hotbed for further QAHE improvements. The family owes its potential to its ferromagnetically (FM) ordered MnBi2Te4 septuple layers (SLs). However, the QAHE realization is complicated in MnBi2Te4 and MnBi4Te7 due to the substantial antiferromagnetic (AFM) coupling between the SLs. An FM state, advantageous for the QAHE, can be stabilized by interlacing the SLs with an increasing number n of Bi2Te3 quintuple layers (QLs). However, the mechanisms driving the FM state and the number of necessary QLs are not understood, and the surface magnetism remains obscure. Here, robust FM properties in MnBi6Te10 (n = 2) with Tc ≈ 12 K are demonstrated and their origin is established in the Mn/Bi intermixing phenomenon by a combined experimental and theoretical study. The measurements reveal a magnetically intact surface with a large magnetic moment, and with FM properties similar to the bulk. This investigation thus consolidates the MnBi6Te10 system as perspective for the QAHE at elevated temperatures. [ABSTRACT FROM AUTHOR]

The complex surface defects induced magnetic properties of lead‐free ferroelectric Bi0.5Na0.5TiO3 (110) materials system are investigated by using the density‐functional theory. Various types of surface defects were considered for calculation, including antisite, vacancies and interstitial defects. The calculated results indicated that a perfect Bi0.5Na0.5TiO3 (110) surface produced zero magnetic moments. The conduction band was mostly contributed from Bi‐6p and Ti‐3d levels, where the valence band was built from O‐2p. The antisite defects where Na replaced for Bi‐site induced nonzero magnetic moments because of unsymmetrical spin O‐2p up and O‐2p down. While, the observation in nonzero magnetic moment of antisite defects Bi substitute for Na‐site were originated from Ti‐3d and Na‐2s. The Na and Bi vacancies on the surface were tuned to the ferromagnetic because of the unsymmetrical contribution of O‐2p, while the Ti and O vacancies were not. The Na and Bi surface interstitials induced the magnetic moments because of the contribution of the difference between Ti‐3d and Bi‐6p, respectively, while the Ti and O surface interstitials not induced the magnetic moments. We expected that our results could help to control chemical defects in new green multiferroic materials for smart electronic devices. [ABSTRACT FROM AUTHOR]

• DFT study of magnetic behavior in 2D V2C-OF MXene and MnO2-adsorbed V2C-OF. • Study showed MnO2-adsorbed V2C shifted from non-magnetic to strong ferromagnetic. • The magnetic moment of 4.48μB for Mn adsorbed V 2 C-OF MXene. The work reports nonmagnetic behavior (0.04 µB) in two-dimensional (2D) V 2 C-OF MXene and ferromagnetism in MnO 2 adsorbed V 2 C-OF MXene. The density functional theory (DFT) calculations were carried out to study the magnetic moments of V 2 C-OF and MnO 2 @V 2 C-OF MXene. The MXene, which is derived from the exfoliation of its parent V 2 AlC MAX phase, shows a good potential to be a ferromagnetic when MnO 2 is adsorbed on it. The V 2 C MXene and MnO 2 adsorbed V 2 C MXene were successfully synthesized, as characterized using X-ray diffraction, showing an increased c-lattice parameter from 22.6 Å to 27.2 Å after MnO 2 adsorption. The DFT study confirmed that MnO 2 adsorbed V 2 C MXene changed from nonmagnetic (in V 2 C MXene) to a strong ferromagnetic with a magnetic moment of 4.48μ B for Mn adsorbed V 2 C-OF MXene. The current work is a step-forward towards understanding of magnetism in two-dimensional materials for future 2D spintronics. [ABSTRACT FROM AUTHOR]

• Pd substitutes Ga at octahedral sites in β-Ga 2 O 3 , confirmed by calculations. • Pd doping stabilizes in negatively charged state under n-type β-Ga 2 O 3 conditions. • Carrier concentration effectively controls ferromagnetism in Pd-doped β-Ga 2 O 3. • Pd d-orbital occupancy influences magnetic states in doped β-Ga 2 O 3. • Pd doping offers insights into spintronic potential of β-Ga 2 O 3. The incorporation of magnetism into semiconductor materials offers promising opportunities for expanding their applications in spintronics. In this study, first-principles calculations are employed to investigate the defect energetics and magnetic properties of Pd-doped β-Ga 2 O 3 , where Pd atoms substitute for Ga atoms. The results reveal that Pd substitution at tetrahedrally coordinated Ga sites incurs significantly higher energy, favoring octahedral coordination instead. Under n-type doping conditions, Pd tends to stabilize in a negatively charged state, contributing to its magnetic behavior. A detailed analysis of the interaction between Pd-Pd pairs demonstrates that ferromagnetism can be effectively controlled by tuning the carrier concentration. Specifically, at optimal n-type carrier densities, a pronounced ferromagnetic interaction is observed, while this effect diminishes with further increases in electron concentration. The findings provide valuable insights into the defect structures, charge states, and magnetic properties of Pd-doped β-Ga 2 O 3 , offering a pathway to manipulating magnetic behavior in semiconductors via carrier concentration modulation, thus paving the way for future spintronic device applications. [ABSTRACT FROM AUTHOR]

In this work, we propose and explore a sensitive technique for investigation of ferromagnetic resonance and corresponding magnetic properties of individual micro-scaled and/or weak ferromagnetic samples. The technique is based on coupling the investigated sample to a high-Q transmission line superconducting resonator, where the response of the sample is studied at eigen frequencies of the resonator. The high quality factor of the resonator enables sensitive detection of weak absorption losses at multiple frequencies of the ferromagnetic resonance. Studying the microwave response of individual micro-scaled permalloy rectangles, we have confirmed the superiority of fluxometric demagnetizing factor over the commonly accepted magnetometric one and have depicted the demagnetization of the sample, as well as magnetostatic standing wave resonance. [ABSTRACT FROM AUTHOR]

Emergent phases at the interfaces in strongly correlated oxide heterostructures display novel properties not akin to those of constituting materials. The interfacial ferromagnetism in (LaMnO3)m/(SrMnO3)n (LMO)m/(SMO)n superlattices (SLs) with antiferromagnetic bulk LMO and SMO layers is believed to be a result of the interfacial charge transfer (CT). By using in situ optical ellipsometry, it is demonstrated directly that CT and emergent magnetism in (LMO)m/(SMO)n SLs are controlled by the LMO/SMO thickness ratio, chosen as m/n = 1 and 2. The enhanced CT in SLs with m/n = 2 favors the high‐TC emergent ferromagnetism with TC = 350–360 K, whereas the reduced CT in m/n = 1 SLs suppresses it yielding TC = 300 K. A complex dependence of the saturation magnetization as a function of interface density Λ = (m + n)−1 with minima at Λ = 0.11 (m/n = 2) and Λ = 0.25 (m/n = 1) was observed and rationalized by the competition of ferromagnetic and antiferromagnetic contributions, originating from the volume of LMO and SMO layers as well as from the LMO/SMO interfaces. The role of epitaxy stress and MnO6 octahedral tilts in the emergent magnetic behavior is discussed. [ABSTRACT FROM AUTHOR]

Actinide materials have various applications that range from nuclear energy to quantum computing. Most current efforts have focused on bulk actinide materials. Tuning functional properties by using strain engineering in epitaxial thin films is largely lacking. Using uranium dioxide (UO2) as a model system, in this work, the authors explore strain engineering in actinide epitaxial thin films and investigate the origin of induced ferromagnetism in an antiferromagnet UO2. It is found that UO2+x thin films are hypostoichiometric (x<0) with in‐plane tensile strain, while they are hyperstoichiometric (x>0) with in‐plane compressive strain. Different from strain engineering in non‐actinide oxide thin films, the epitaxial strain in UO2 is accommodated by point defects such as vacancies and interstitials due to the low formation energy. Both epitaxial strain and strain relaxation induced point defects such as oxygen/uranium vacancies and oxygen/uranium interstitials can distort magnetic structure and result in magnetic moments. This work reveals the correlation among strain, point defects and ferromagnetism in strain engineered UO2+x thin films and the results offer new opportunities to understand the influence of coupled order parameters on the emergent properties of many other actinide thin films. [ABSTRACT FROM AUTHOR]

The layered van der Waals metallic material Fe5−xGeTe2, which has near room-temperature itinerant ferromagnetism, offers unprecedented opportunities to explore exotic phenomena and functionalities as well as prospective uses in spintronic or quantum devices. However, the intriguing magnetic ground state of Fe5−xGeTe2 is quite complicated and remains controversial. In this work, we investigate the magnetic ordering transitions in Fe5−xGeTe2 nanoflakes through magneto-transport measurements. The anomalous Hall resistance increases with rising temperature, reaching its maximum at 100 K. Meanwhile, a clear butterfly-shaped magnetoresistance hysteresis was observed with opposite dependence on the switching field around this critical temperature. All experimental results point to the scenario that Fe5−xGeTe2 transitions from the paramagnetic to ferromagnetic state at 265 K and then evolves to a ferrimagnetic state at 100 K. Our work promotes the understanding of magnetism in Fe5−xGeTe2 and motivates further efforts to develop room-temperature spintronic devices based on Fe5−xGeTe2. [ABSTRACT FROM AUTHOR]

Van der Waals heterostructures offer great versatility to tailor unique interactions at the atomically flat interfaces between dissimilar layered materials and induce novel physical phenomena. By bringing monolayer 1 T' WTe2, a two-dimensional quantum spin Hall insulator, and few-layer Cr2Ge2Te6, an insulating ferromagnet, into close proximity in an heterostructure, we introduce a ferromagnetic order in the former via the interfacial exchange interaction. The ferromagnetism in WTe2 manifests in the anomalous Nernst effect, anomalous Hall effect as well as anisotropic magnetoresistance effect. Using local electrodes, we identify separate transport contributions from the metallic edge and insulating bulk. When driven by an AC current, the second harmonic voltage responses closely resemble the anomalous Nernst responses to AC temperature gradient generated by nonlocal heater, which appear as nonreciprocal signals with respect to the induced magnetization orientation. Our results from different electrodes reveal spin-polarized edge states in the magnetized quantum spin Hall insulator. Van der Waals heterostructures allow for the integration of several materials with different properties in the one heterostructure. Here, Li et al combine a quantum spin hall insulator, WTe2, with an insulating ferromagnet, Cr2Ge2Te6, in a van der Waals heterostructure, with resulting proximity-induced magnetism in the WTe2 layer leading to an anomalous Hall and Nernst effect. [ABSTRACT FROM AUTHOR]

The effect on the superconductivity of the partial replacement of one magnetic rare-earth element (Dy) by another (Er) in rhodium borides Dy1–xErxRh3.8Ru0.2B4 with x = 0, 0.2, 0.4 is studied. It was found that in Dy1–xErxRh3.8Ru0.2B4, with increasing Er content, the temperature of the superconducting transition increases significantly: from 3.7 K for x = 0 to 6 K for x = 0.4. It was demonstrated that the replacement of magnetic Er3+ with nonmagnetic Y3+ in the isostructural compounds Dy0.6Er0.4Rh3.8Ru0.2B4 (Tc ≈ 6 K) and Dy0.6Y0.4Rh3.85Ru0.15B4 (Tc ≈ 7 K) does not lead to a significant change in the temperature of the superconducting transition. The suppression of the superconducting state by the magnetism of rare-earth elements is not observed down to 1.5 K the lowest available temperature in the experiment. [ABSTRACT FROM AUTHOR]

The effect on the superconductivity of the partial replacement of one magnetic rare-earth element (Dy) by another (Er) in rhodium borides Dy1–xErxRh3.8Ru0.2B4 with x = 0, 0.2, 0.4 is studied. It was found that in Dy1–xErxRh3.8Ru0.2B4, with increasing Er content, the temperature of the superconducting transition increases significantly: from 3.7 K for x = 0 to 6 K for x = 0.4. It was demonstrated that the replacement of magnetic Er3+ with nonmagnetic Y3+ in the isostructural compounds Dy0.6Er0.4Rh3.8Ru0.2B4 (Tc ≈ 6 K) and Dy0.6Y0.4Rh3.85Ru0.15B4 (Tc ≈ 7 K) does not lead to a significant change in the temperature of the superconducting transition. The suppression of the superconducting state by the magnetism of rare-earth elements is not observed down to 1.5 K the lowest available temperature in the experiment. [ABSTRACT FROM AUTHOR]

(In,Fe)Sb layers with a Fe content up to 13 at. % have been grown on (001) GaAs substrates using the pulsed laser deposition. Transmission electron microscopy shows that the layers are epitaxial and free of second-phase inclusions. The observation of hysteretic magnetoresistance curves at temperatures up to 300K and the investigations of magnetic circular dichroism reveal that the Curie point lies above room temperature. The resonant character of magnetic circular dichroism confirms the intrinsic ferromagnetism in the (In,Fe)Sb matrix. We suggest that the ferromagnetism of the (In,Fe)Sb matrix is not carrier-mediated and is apparently determined by the mechanism of superexchange interaction between Fe atoms. [ABSTRACT FROM AUTHOR]

We theoretically investigate the electronic and magnetic properties of the recently reported cubic and orthorhombically (Ortho.) distorted phases of PbMoO3, a 4d transition-metal perovskite oxide with almost half-filled t2g states. Our spin-polarized bare generalized gradient approximation results exhibit that the cubic phase is of low energy structure than the Ortho. one. However, on-site Coulomb repulsion in the range of 3.3 eV≤Ueff≤4.5 eV inclusion on Mo 4d orbitals reveals that at each value of Ueff, the Ortho. phase is more stable than the cubic one and with the increase in Ueff, both phases show more stability. We find a non-magnetic n-type conductivity with a high charge carrier density of ~1022cm-3 in both phases. Interestingly, a non-magnetic to magnetic phase transition occurs at Ueff=3.8 eV and 3.5 eV for the cubic and Ortho. phases, respectively. Moreover, a half-metallic ferromagnetic state is obtained at Ueff=4.1 eV and 4.3 eV for the cubic and Ortho. phases, respectively. Calculations also indicate a strong orbital hybridization between Pb 6p and Mo 4d, with a significant contribution of O 2p states. All findings are confirmed by the Yukawa screened Perdew-Burke-Ernzerhof 0 (YS-PBE0) hybrid functional. This work provokes further experimental investigations of magnetic properties of PbMoO3. [ABSTRACT FROM AUTHOR]

• Anomalous magnetization due to 4 f hybridization among Nd systems has been less demonstrated compared to Ce systems. • We bring out that the magnetism of Nd compounds in AlB 2 -derived ternary family is exotic due to Nd 4 f hybridization. • Exhaustive studies based on bulk measurements are reported here for the first time for Nd 2 RhSi 3. • Nd 2 RhSi 3 is shown to be ferromagnetic (T C = 16.5 K), unlike antiferromagnetism for other members of this family. A complex magnetism below T C. • Additional unique feature is the observation of cluster magnetism with spin-glass dynamics above T C. • Disorder in exchange interaction due to geometry of Nd atoms arrangement appears to play a key role on exotic magnetism. The compound, Nd 2 PdSi 3 belonging to R 2 PdSi 3 family (R = rare-earths) has been known to exhibit exotic behavior due to unusual Nd 4 f -hybridization. Here, we study the electronic properties of Nd 2 RhSi 3 employing ac and dc magnetization, heat-capacity, electrical resistivity and magnetoresistance measurements, as Nd 4 f -hybridization is expected to be slightly different due to the changes in the 4 d element. The experimental results establish that, like the Pd analogue, this compound also exhibits ferromagnetic ordering at a rather high temperature of 16.5 K, unlike many other rare-earth members of this family which are antiferromagnetic, with a complex magnetism at further lower temperatures (< ∼10 K). There are differences in the measured properties with respect to the Pd analogue, the most important one being the observation of spin-glass features at a temperature significantly higher than the Curie temperature. This is attributed to a gradual evolution of cluster magnetism with decreasing temperature. We infer that the changes in Nd 4 f hybridization due to Rh 4 d (instead of Pd 4 d) plays a role in some fashion for such differences. These properties are attributed to the competing magnetic ground states due to geometrical frustration arising out of triangular arrangement of Nd ions with a bond disorder. [ABSTRACT FROM AUTHOR]

We investigate the properties of spinel structure ZnCr 2 Te 4 as a candidate cubic material for giant transport anisotropy. We find that this cubic spinel ZnCr 2 Te 4 phase is a ferromagnetic semimetal and that it is metastable, with an enthalpy only slightly above that of the competing phases, ZnTe and Cr 2 Te 3. The Fermi surface is derived from bands of opposite spin that cross very close to the Fermi level. This results in an unusual situation where the interplay of spin orbit coupling and magnetism substantially reconstructs the Fermi surface in a way that depends on magnetization direction. This leads to a prediction of unusual anisotropic transport behavior in a cubic material. For magnetization along [001], we find σ z z (20 K)/ σ x x (20 K) = 1.27. This is a large anisotropy for a cubic material. At a temperature of 200 K the anisotropy decreases to σ z z (200 K)/ σ x x (200 K) = 1.11 presuming the ferromagnetism remains intact. For the [111] magnetization direction, the conductivity anisotropy is low at 20 K, but increases with temperature to a value σ ∥ (200 K)/ σ ⊥ (200 K) = 1.10 at 200 K, where ∥ and ⊥ denote conductivity along the [111] magnetization direction, and perpendicular to it, respectively. • Cubic spinel ZnCr 2 Te 4 is a metastable ferromagnetic semimetal. • ZnCr 2 Te 4 has bands of opposite spin character that intersect very close to the Fermi level. • The intersecting bands lead to a Fermi surface that is strongly anisotropic due to spin-orbit, even though the material is cubic. • This anisotropy of the Fermi surface leads to an unusual transport anisotropy with possible applications. [ABSTRACT FROM AUTHOR]

The electronic and magnetic properties of ZnO: (Mn, N) and the effect of vacancy defect on its magnetism were studied systematically, using the first-principle based on density functional theory (DFT). The results show that the introduction of the N atom would make the coupling between two Mn atoms turn into the ferromagnetic coupling, which resulted from a hybridization between Mn 3d and N 2p electrons. Mn (MnZn) and N (NO) atoms have a tendency toward staying close to each other to form the –Mn–N–Mn– complex with two Mn–N bonds. Furthermore, VZn or VO are the easiest to form at the first-nearest neighbor or at the second-nearest neighbor of the –Mn–N–Mn– complex, at which, VO basically has no influence on the magnetism, while VZn would weaken ferromagnetism. [ABSTRACT FROM AUTHOR]

Research interests in recent years have expanded into quantum materials that display novel magnetism incorporating strong correlations, topological effects, and dimensional crossovers. Fe3GeTe2 represents such a two-dimensional van der Waals platform exhibiting itinerant ferromagnetism with many intriguing properties. Up to date, most electronic transport studies on Fe3GeTe2 have been limited to its anomalous Hall responses while the longitudinal counterpart (such as magnetoresistance) remains largely unexplored. Here, we report a few unusual transport behaviors on thin flakes of Fe3GeTe2. Upon cooling to the base temperature, the sample develops a resistivity upturn that shows a crossover from a marginally â€"ln T to a â€" T 1/2 dependence, followed by a lower-temperature deviation. Moreover, we observe a negative and non-saturating linear magnetoresistance when the magnetization is parallel or antiparallel to the external magnetic field. The slope of the linear magnetoresistance also shows a nonmonotonic temperature dependence. We deduce an anomalous contribution to the magnetoresistance at low temperatures with a scaling function proportional â€" HT 1/2, as well as a temperature-independent linear term. Possible mechanisms that could account for our observations are discussed. [ABSTRACT FROM AUTHOR]

Research interests in recent years have expanded into quantum materials that display novel magnetism incorporating strong correlations, topological effects, and dimensional crossovers. Fe3GeTe2 represents such a two-dimensional van der Waals platform exhibiting itinerant ferromagnetism with many intriguing properties. Up to date, most electronic transport studies on Fe3GeTe2 have been limited to its anomalous Hall responses while the longitudinal counterpart (such as magnetoresistance) remains largely unexplored. Here, we report a few unusual transport behaviors on thin flakes of Fe3GeTe2. Upon cooling to the base temperature, the sample develops a resistivity upturn that shows a crossover from a marginally â€"ln T to a â€" T 1/2 dependence, followed by a lower-temperature deviation. Moreover, we observe a negative and non-saturating linear magnetoresistance when the magnetization is parallel or antiparallel to the external magnetic field. The slope of the linear magnetoresistance also shows a nonmonotonic temperature dependence. We deduce an anomalous contribution to the magnetoresistance at low temperatures with a scaling function proportional â€" HT 1/2, as well as a temperature-independent linear term. Possible mechanisms that could account for our observations are discussed. [ABSTRACT FROM AUTHOR]

The structure and magnetism of a Mn trimer adsorbed on iridium-doped graphene are studied using density functional theory calculations. Our calculation results show that the Mn trimer prefers to locate on top of the Ir atom and forms a fully exposed high-symmetry configuration with large binding energy and hardness of rotation. The ferromagnetic ordering of the Mn trimer fully exposed the on iridium-doped graphene is enhanced five times compared to a free Mn trimer. Our study shows that the enhancement originates from the fixed long bond and the C 3 v symmetry of the Mn trimer constrained by the iridium-doped graphene. [ABSTRACT FROM AUTHOR]

Modifying the properties of graphene has gained wide interest for a plethora of potential applications, including spintronics. One approach has demonstrated that proton irradiation can induce ferromagnetism in graphene as well as in graphite. However, little is known about how the protons interact with graphene, the mechanism that creates the ferromagnetism, or whether the protons remain in the graphene. Here we report an investigation, broadly relevant to graphitic carbon, using low-energy (360–2000 eV) ions of hydrogen, deuterium, and helium implanted into multilayer epitaxial graphene. Complementary x-ray and neutron reflectivity demonstrate that essentially all of the implanted hydrogen remains chemisorbed in graphene. In situ x-ray diffraction reveals significantly different rates of interlayer expansion of the multilayer graphene. Analysis of these data demonstrates that the interlayer expansion arises entirely from the interstitials created by the ions and not from hydrogen that remains in the graphene. The results also establish a quantitative measure of the layer expansion due to carbon interstitials. Magnetometry and x-ray diffraction studies show that the magnetic moment relates to the amount of interstitial carbon rather than the amount of hydrogen, demonstrating that the induced room-temperature ferromagnetism arises directly from the disrupted bonding of the carbon lattice. [Display omitted] [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) ferromagnetic materials have been discovered with tunable magnetism and orbital-driven nodal-line features. Controlling the 2D magnetism in exfoliated nanoflakes via electric/magnetic fields enables a boosted Curie temperature (T C) or phase transitions. One of the challenges, however, is the realization of high T C 2D magnets that are tunable, robust and suitable for large scale fabrication. Here, we report molecular-beam epitaxy growth of wafer-scale Fe3+XGeTe2 films with T C above room temperature. By controlling the Fe composition in Fe3+XGeTe2, a continuously modulated T C in a broad range of 185–320 K has been achieved. This widely tunable T C is attributed to the doped interlayer Fe that provides a 40% enhancement around the optimal composition X = 2. We further fabricated magnetic tunneling junction device arrays that exhibit clear tunneling signals. Our results show an effective and reliable approach, i.e. element doping, to producing robust and tunable ferromagnetism beyond room temperature in a large-scale 2D Fe3+XGeTe2 fashion. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides have made a tremendous progress during last two decades owing to their use in technologically important applications like electronics, optoelectronics, magnetism, and energy storage applications. Herein, we present synthesis of nanosheets of Ni9S8/MoS2 hybrid nanosheet using the hydrothermal method and induction of ferromagnetism is being reported at room temperature as well. Magnetic properties of both pristine MoS2 and hybrid Ni9S8/MoS2 were probed using experimental techniques; it is revealed that unlike pristine MoS2, hybrid Ni9S8/MoS2 shows ferromagnetic behavior both at room temperature and at low temperature (5 K). It is proposed that ferromagnetism in this hybrid structure is being caused by the introduction of Ni atoms. [ABSTRACT FROM AUTHOR]

The substitution of rare-earth ions has been recognized as an effective way to modify the multiferroic properties, especially to realize the electric field-controlled magnetism in BiFeO3 ceramics, in which the symmetry modulation of R3c/Pna21 and the unlocked ferromagnetism through breaking the cycloidal spin structure are the key issues. Here, the enhancement of ferroelectric polarization and weak ferromagnetism are investigated in Bi1−xLaxFeO3 ceramics together with the magnetoelectric coupling coefficient αME with the development of the Pna21 phase. The expected electric field-controlled magnetism is achieved at the phase boundary through the electric field-induced transition of Pna21/R3c, where the variation of magnetization reaches 34.18 emu/mol (58.95%) at x = 0.18 after poling. [ABSTRACT FROM AUTHOR]

BaTiO 3 ceramics doped with double perovskite Sr 2 KMoO 6 (BT-SKM) are fabricated via solid-state reaction technology. The effects of SKM dopants on the structure, band gap and electrical/magnetic properties of BT are systematically studied. XRD and Raman spectra analysis show polycrystalline perovskite structure of the samples, which confirms the structural changes. With the addition of SKM dopants, the grain size of the samples decreases significantly. The band gaps of doped BT samples reduce, and the minimum band gap of BT-SCM is 1.77 eV, which is apparently reduced compared with the band gap of pure BT of 3.22 eV. However, the ferroelectric properties are weakened in samples doped with SKM. This ascribes to the introduction of more oxygen vacancies by dopants, which impedes the switching of domains, resulting in deterioration of ferroelectric properties. Furthermore, ferromagnetism of BT-SNM is observed, which may be attributed to the long-range exchange interaction between Ni2+ ions and oxygen vacancies. These results reveal the potential applications of these perovskite oxides in photovoltaic and memory devices. [ABSTRACT FROM AUTHOR]

This year the discovery of femtosecond demagnetization by laser pulses is 20 years old. For the first time, this milestone work by Bigot and coworkers gave insight directly into the time scales of microscopic interactions that connect the spin and electron system. While intense discussions in the field were fueled by the complexity of the processes in the past, it now became evident that it is a puzzle of many different parts. Rather than providing an overview that has been presented in previous reviews on ultrafast processes in ferromagnets, this perspective will show that with our current depth of knowledge the first applications are developed: THz spintronics and all-optical spin manipulation are becoming more and more feasible. The aim of this perspective is to point out where we can connect the different puzzle pieces of understanding gathered over 20 years to develop novel applications. Based on many observations in a large number of experiments. Differences in the theoretical models arise from the localized and delocalized nature of ferromagnetism. Transport effects are intrinsically non-local in spintronic devices and at interfaces. We review the need for multiscale modeling to address the processes starting from electronic excitation of the spin system on the picometer length scale and sub-femtosecond time scale, to spin wave generation, and towards the modeling of ultrafast phase transitions that altogether determine the response time of the ferromagnetic system. Today, our current understanding gives rise to the first usage of ultrafast spin physics for ultrafast magnetism control: THz spintronic devices. This makes the field of ultrafast spin-dynamics an emerging topic open for many researchers right now. [ABSTRACT FROM AUTHOR]

Ferromagnetic semiconductors discovered in 2D materials open an avenue for highly integrated and multifunctional spintronics. The Curie temperature (TC) of existing 2D ferromagnetic semiconductors is extremely low and the modulation effect of their magnetism is limited compared with their 2D metallic counterparts. The interfacial effect is found to effectively manipulate the 3D magnetism, providing a unique opportunity for tailoring the 2D magnetism. Here, it is demonstrated that the TC of a 2D ferromagnetic semiconductor Cr2Ge2Te6 (CGT) can be enhanced by 130% (from ≈65 K to above 150 K) when adjacent to a tungsten layer. The interfacial W–Te bonding contributes to the TC enhancement with a strong perpendicular magnetic anisotropy, guaranteeing efficient magnetization switching by the spin‐orbit torque with a low current density at 150 K. Distinct from the rapid attenuation in conventional magnets, the interfacial effect exhibits a weak dependence on CGT thickness and a long‐distance effect (more than 10 nm) due to the weak interlayer coupling inherent to 2D magnets. This work not only reveals a unique interfacial behavior in 2D materials, but also advances the process toward practical 2D spintronics. [ABSTRACT FROM AUTHOR]

Cerium oxides (ceria) are materials that exhibit weak, room-temperature ferromagnetism without d-electrons. The latter are usually responsible for magnetism in a variety of other oxide compounds, but the underlying mechanism for such a magnetic response in ceria without the delectrons (d 0 -magnetism) is still under debate. A possible explanation is Zener double-exchange, where itinerant electrons polarize the localized spins via Hund-coupling as they hop from site to site. Here, we report magnetization and spin-spin correlation results using various values of the Hund-coupling in a one-orbital double-exchange model with Ising spins. In the real material with formula CeO2−x, the oxygen-deficient sites are denoted by x. These sites are related to the density of tetravalent cerium spins (the Ising spin background in our model), which we denoted as and set at N = 0.50 in our simulations. Our results at this value of localized spin concentration show ferromagnetic tendencies at low carrier densities (n = 0.25). However, ferromagnetism is lost at intermediate carrier concentrations (n = 0.50) due to charge localization at high temperatures, as evident from density of states calculations and Monte Carlo snapshots. To our knowledge, our study based on a realistic Zener-type double exchange mechanism is a first in the study of magnetism in cerium oxides. Our results are also consistent with previous studies using similar Hamiltonians in the context of diluted magnetic semiconductors, where Heisenberg spins were used. [ABSTRACT FROM AUTHOR]

Bulk and nanoparticle powders of LaCoO3 (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T ≈ 85 K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, To≈40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co3O4 impurity phase, which induces tensile strain on the LCO lattice. A core-interface model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases.

Bulk La(w)CoO(3) particles with w = 1.1, 1.0, 0.9, 0.8, and 0.7 were synthesized using starting materials with varying molar ratios of La(2)O(3) and Co(3)O(4). The resulting particles are characterized as LaCoO(3) crystals interfaced with a crystalline Co(3)O(4) phase. X-ray and neutron scattering data show little effect on the average structure and lattice parameters of the LaCoO(3) phase resulting from the Co(3)O(4) content, but magnetization data indicate that the amount of Co(3)O(4) strongly affects the ferromagnetic ordering at the interfaces below TC ≈ 89 K. In addition to ferromagnetic long-range order, LaCoO(3) exhibits antiferromagnetic behavior with an unusual temperature dependence. The magnetization for fields 20 Oe ⩽ H ⩽ 5 kOe is fit to a combination of a power law ((T - TC)/TC)(β) behavior representing the ferromagnetic long-range order and sigmoid-convoluted Curie-Weiss-like behavior representing the antiferromagnetic behavior. The critical exponent β = 0.63 ± 0.02 is consistent with 2D (surface) ordering. Increased Co(3)O(4) correlates well to increased ferromagnetism. The weakening of the antiferromagnetism below T ≈ 40 K is a consequence of the lattice reaching a critical rhombahedral distortion as T is decreased for core regions far from the Co(3)O(4) interfaces. We introduce a model that describes the ferromagnetic behavior of the interface regions and the unusual antiferromagnetism of the core regions.

We report on the epitaxial growth and magnetic properties of Cr2O3 thin films grown on r-sapphire substrate using pulsed laser deposition. The X-ray diffraction (XRD) (2θ and φ) and TEM characterization confirm that the films are grown epitaxially. The r-plane (0112) of Cr2O3 grows on r-plane of sapphire. The epitaxial relations can be written as [0112] Cr2O3 || [0112] Al2O3 (out-of-plane) and [H20] Cr2O3 || [1120] Al2O3 (in-plane). The as-deposited films showed ferromagnetic behavior up to 400 K but ferromagnetism almost vanishes with oxygen annealing. The Raman spectroscopy data together with strain measurements using high resolution XRD indicate that ferromagnetism in r-Cr2O3 thin films is due to the strain caused by defects, such as oxygen vacancies. [ABSTRACT FROM AUTHOR]

Polycrystalline YMn2-xTixO5 (x=0.00-0.05) samples with partial substitution of Mn by Ti are prepared in order to modulate the multiferroicity of YMn2O5. It is revealed that the substituting Ti ions are in the Ti4+ valence state and prefer to occupy the Mn4+ sites. The lattice structure has slight volume expansion upon the Ti substitution, although the symmetry remains unchanged. A proper Ti4+ substitution surprisingly allows significant enhancement of ferroelectric polarization and appearance of weak ferromagnetism. It is suggested that the substitution induced Ti4+O6 octahedra and modulated exchange-striction are possibly responsible for the enhanced ferroelectricity and improved ferromagnetism. [ABSTRACT FROM AUTHOR]