Ab initio investigation of structural stability, magnetic ground state, and mechanical anisotropy of the CoCrFeNi high-entropy alloy

Achieving reversible ferroic control over distinct compensated magnetic states is of fundamental importance for developing reconfigurable spintronic functionalities, yet remains a nontrivial challenge. Here we predict that layered hybrid-improper multiferroics provide a broadly applicable platform for such interconversion in the monolayer or few-layer limit. Using monolayer K3Mn2Cl7 as a representative example, whose bulk multiferroicity has been experimentally established, we show that its magnetic ground state is an insulating compensated magnet with in-plane ferroelectric polarization, and that ferroic control can drive reversible multiferroic phase transitions among multiple types of compensated magnets. The (anti)ferroelectric states here retain spin degeneracy in the nonrelativistic limit but acquire full-space persistent spin texture and transport responses. Interestingly, both ferroelectric and antiferroelectric states exhibit sign-reversible Hall transport without exchange splitting reversal found in conventional compensated magnets, revealing an unexplored form of magnetoelectric coupling. These results establish layered hybrid-improper multiferroics as promising building blocks for programmable spintronics.

Abstract Unconventional magnetic materials including non-collinear antiferromagnets, p-wave magnets and altermagnets, are an emerging frontier for quantum spintronics and hybrid quantum devices. Critical to the application of these materials is control over the magnetic domain state, as their unique, symmetry-driven properties vanish in a multi-domain limit. However, the mechanisms governing domain formation in materials with compensated local moments remain poorly understood. In this work, we examine the ferrimagnetic to non-collinear antiferromagnetic phase transition of Mn3NiN using scanning nitrogen-vacancy centre magnetometry. We provide nanoscale mapping of the magnetic domain evolution on cooling and correlate the local stray fields with global magnetometry and anomalous Hall effect measurements. We observe the formation of a disordered, dendritic domain structure whose roughness is quantified using its fractal dimension. The fractal dimension steadily increases on cooling through the transition, saturating at a value of ~ 1.55 in the non-collinear phase, but the domain area distribution does not show any significant changes. We show this behaviour cannot be explained by the balance of demagnetisation energy and domain wall energy, and conclude elastic contributions and defects are a critical factor to explain the domain size.

Laser‐induced switching of magnetization between multiple magnetic states has tremendous potential for data recording and storage applications. As a nonthermal phenomenon, photo‐magnetic switching stands out from various discovered switching mechanisms with its unparalleled energy efficiency. Dielectric rare‐earth iron garnet cubic crystals, where it has been observed, enrich magnetization dynamics with high symmetry and complicated magnetic anisotropy landscape, enabling storage of multiple bits of information in a single magnetic domain. In this work we demonstrate methods to control the photo‐magnetic torque, which sets the magnetization into motion and eventually determines both its trajectory and destination. We use the formalism based on Landau–Lifshitz–Gilbert dynamics with an effective anisotropy field originating in the photo‐magnetism and analyze the methods to modify the torque sign and magnitude. In particular, we demonstrate how varying equilibrium magnetization, light polarization, and using plasmonic excitations in metal‐dielectric hybrids enable steady control of the photo‐magnetic dynamics, which is key for the multistate switching. Our work outlines promising directions for future research towards highly efficient magnetic recording at the nanoscale.

Disentangling non-spin-dependent and spin-dependent contributions to magnetic field-induced oxygen evolution reaction (OER) enhancement remains challenging due to the difficulty in quantifying magnetic flux density near catalytic surfaces, which depends on both the applied field and the intrinsic magnetic properties of the catalyst. Herein, 2:17-type samarium-cobalt magnets (Sm2Co17) with different initial magnetization states were evaluated in an electromagnet-integrated flow cell, employing magnetization cycle analysis to elucidate how intrinsic magnetic properties and magnetization state influence OER enhancement. Analysis of the potential shift (ΔE) throughout a complete magnetization cycle reveals butterfly shaped hysteresis, with characteristic loop features providing mechanistic insights. Bulk magnetic properties influence the loop contour via spin-pinning effects, whereas surface composition and magnetization state govern the linear ΔE shifts. The slope (κ) of the linear ΔE shifts serves as a descriptor of the catalytic surface response to magnetic field, enabling ΔE determination at a given field strength. Together, κ and the butterfly-shaped loop characteristics provide a potential analytical framework for quantifying magnetic field-induced OER enhancement and may offer insights into the magnetic properties of catalytic surfaces that emerge exclusively under OER conditions.

Abstract The properties of magnons hosted in the pristine and doped two-dimensional Ti 2 C MXene are theoretically explored as a function of the vanadium doping concentration. By replacing Titanium (Ti) ions with vanadium (V) ones, we obtain the corresponding magnon bands for the different magnetic states formed by systematically varying the vanadium (V) doping concentration. Linear response theory is used to compute the magnon transport coefficients as a function of the doping concentration and temperature. We found that doping has a considerable effect on the symmetries present in the system, allowing for changes in the spin wave stiffness tensor. As a result, a Hall-like transverse magnon transport emerges despite the absence of Berry curvature or topological signatures, whose origin lies in changes in the crystal main axis, thereby introducing anisotropic magnon transport. Our results suggest that doping magnetic Ti 2 C MXenes with vanadium could pave the way towards MXenes-based spin caloritronic systems with tunable anisotropy and directional heat/spin control.

Hyperbolic metasurfaces with hyperbolic dispersion have gained significant attention due to their unprecedented capabilities to manipulate the propagation of surface plasmon polaritons, such as non-divergent diffraction and polarization-controlled signal routing based on the plasmonic spin Hall effect. However, thus far, selective routing of surface waves has only been observed with the mechanism of plasmonic spin-orbit coupling, which depends on the polarization of light and the hyperbolic iso-frequency contours. Here, we propose and experimentally demonstrate symmetry-dependent selective electric and magnetic surface wave excitation around the geometric phase transition frequency with coexisting transverse electric and transverse magnetic polarization states. Effective medium theory and S-parameter retrieval process are further utilized to analyze the electromagnetic responses and dispersion characteristics of the designed asymmetric hyperbolic metasurface. These results open up a new avenue, to our knowledge, to realize integrated plasmonic devices, holding potential for applications in areas including imaging, sensing, and quantum information science.

Altermagnets have attracted considerable attention for uniting the advantages of ferromagnets and antiferromagnets and for their promise in advancing spintronics. However, investigations focused on tuning the properties of two-dimensional altermagnets, particularly regarding magnetic phase transition, electronic properties, and anomalous Hall conductivity, remain comparatively limited. Here, we propose an approach to manipulate the magnetic ground state, metal to half-metal transition, Rashba spin splitting, and anomalous Hall conductivity of an altermagnet by ferroelectric reversal. To address experimental fabrication and application needs, we systematically investigated three typical stacking configurations under three strain conditions in the Ti2Se2S/PbTe van der Waals heterostructures, confirming the feasibility of this approach. Under the strong compressive strain, the ferroelectric polarization switching not only tunes the transition from the altermagnetic to ferromagnetic states but also regulates the magnitude and direction of the anomalous Hall conductivity. Importantly, interface effects can induce pronounced Rashba splitting in all altermagnetic states. When the strain reaches a moderate compressive level, although the ferromagnetic state persists under all polarization directions, switching the ferroelectric polarization induces a half-metal to metal transition. While the anomalous Hall conductivity shows little change, the Berry curvature is fully reconfigured by polarization switching. Without applied strain, all configurations show a ferromagnetic metallic state. The dramatic change in anomalous Hall conductivity upon polarization switching originates from a modification in the occupation of spin-polarized states. Our findings provide a direction for investigating altermagnetic devices with implications for nonvolatile, ultrafast, and low-power spintronic devices.

In d0 ferromagnets, where magnetism arises from spin-polarized p orbitals of light anions, magnetocrystalline anisotropy energy (MAE) is generally weak due to limited spin-orbit coupling (SOC) in the magnetic states. In this work, we investigate the magnetic anisotropy in the two-dimensional d0 ferromagnetic multiferroic monolayer TiCdO4 using first-principles calculations, revealing a novel mechanism for the emergence of MAE. We demonstrate that the heavy nonmagnetic cation Cd, despite its 4d states being well below the Fermi level, plays a crucial role in mediating SOC effects. The hybridization between Cd d states and O 2p orbitals near the Fermi level enhances SOC between Cd and O, thereby contributing to the MAE. Notably, this hybridization induces substantial SOC from Cd to the O p orbitals, which drives the MAE in this d0 ferromagnet. Furthermore, we reveal that the ferroelectric phase transition from the centrosymmetric metallic P2/m phase to the polar insulating P1 phase strengthens a specific Cd-O bond due to a reduced bond length, leading to an increased contribution to the MAE from a particular oxygen site. These findings provide novel theoretical insights into magnetic anisotropy in d0 ferromagnetic multiferroics, demonstrating how the interplay between heavy nonmagnetic cations and oxygen p orbitals can induce significant MAE through orbital hybridization. Our results suggest a new pathway for controlling MAE in d0 systems by tuning cation-anion interactions, advancing the design of multiferroic materials.

Co3O4 is an important transition-metal oxide with wide applications in catalysis and energy storage. In this work, using evolutionary ab initio structural searches combined with first-principles calculations, we systematically investigated its structural stability, phase transitions, magnetic evolution and electronic properties within the pressure range of 0-100 GPa. Our results show that the cubic Fd3̄m phase first transforms into an orthorhombic Fddd structure through a symmetry-lowering distortion driven by compressibility mismatch between Co2+O4 and Co3+O6 polyhedra. Pressure-enhanced Co-O hybridization and broadened 3d bandwidth modify the exchange interactions, driving the magnetic ground state from antiferromagnetic (Fd3̄m) to ferromagnetic (Fddd). A subsequent first-order transition to a monoclinic P21/c phase involves full CoO6 coordination, lattice densification, and charge redistribution between Co2+ and Co3+, ultimately leading to magnetic collapse. Based on these results, a detailed temperature-pressure phase diagram is constructed. These findings not only elucidate the intrinsic coupling among the crystal structure, coordination environment, and magnetism in Co3O4 under high pressure but also provide insight into phase transitions in spinel-type transition-metal oxides.

Quantum spin-liquid (QSL) ground state emerges in frustrated magnetic systems where competing interactions suppress long-range magnetic ordering. TbInO3, a hexagonal perovskite, shows QSL behaviour due to geometrical frustration and strong spin-orbit coupling present in it. Here, we report the strain-driven modification of the magnetic ground state and the enhancement of magnetic frustration at milli-Kelvin (mK) temperature (<1 K) in the TbInO3epitaxial thin film, grown on MgO (100) substrate. We observe a Curie-Weiss crossover at 1-30 K temperature, strong antiferromagnetic interactions, along with the absence of long-range ordering down to 400 mK, consistent with a QSL ground state. Notably, the thin film exhibits a significantly enhanced effective moment in the mK range compared to the bulk, attributed to strain-induced modification of the exchange pathway among Tb3+ions. This impact broadens the QSL state's temperature range to lower temperatures and enhances magnetic frustration in the temperature-field phase space. Further, the first-principles calculation also supports the enhancement of frustration in thin film. These findings demonstrate that strain-induced tuning of exchange interactions can enhance the magnetic frustration, offering a route to stabilise QSL phases down to lower temperatures in hexagonal perovskite thin films.

The recent emergence of altermagnetism has enriched the classification of magnetic states. The symmetry constrained even-parity and odd-parity altermagnets are mainly limited to collinear and noncollinear spins in two- and three-dimensional materials. In this work, guided by the symmetry classification, we propose a general strategy for designing unconventional p-wave altermagnets in one-dimensional (1D) collinear antiferromagnets with the switchable spin-splitting under circularly polarized light, also extendable to the odd-parity altermagnets in two-dimensional (2D) collinear antiferromagnets. First-principles calculations on experimentally synthesized 1D and 2D triangulene crystals further validate our design principles, realizing the extrinsic p-wave and f-wave altermagnets. By coupling 2D altermagnetic triangulene crystals to s-wave superconductors, the high-Chern-number topological superconductivity can be achieved within spin-splitting energy windows. Our work introduces a new mechanism to engineer light-induced 1D and 2D odd-parity altermagnets and provides a molecular platform to explore the metal-free altermagnetism in π-conjugated covalent organic frameworks.

The pursuit of fully spin-polarized currents remains a central challenge in spintronics. Zigzag graphene nanoribbon/hexagonal boron nitride (ZGNR/h-BN) heterojunctions offer a promising platform due to their stabilized edge states and tunable electronic properties. However, their inherent antiferromagnetic (AFM) order and limited means of external-field-free control hinder practical applications. Here, we demonstrate a deterministic strategy to achieve field-free manipulation of both magnetic order and electronic phases in ZGNR/h-BN heterojunctions by embedding pentagon-octagon (558) topological line defects. Density functional theory calculations reveal that this defect engineering spontaneously drives a transition from the pristine AFM state to a ferrimagnetic (FiM) ground state, originating from spin polarization reconstruction at the defect sites and asymmetric edge moments. Furthermore, the electronic properties exhibit programmable phase transitions: the system evolves from a conventional half-metal to a Dirac half-semimetal with Fermi velocities up to 3 × 105 m s-1, and eventually to a full metal, as the ZGNR width increases. Remarkably, shifting the defect position enables continuous modulation of the spin-down bandgap (0-0.18 eV) and can even induce a ferromagnetic state. The FiM order and half-metallicity are robust under biaxial strain within ±5%, while a transition to ferromagnetism can be triggered by specific uniaxial strains. This work establishes a versatile pathway, integrating defect engineering with heterojunction design, for the on-demand, external-field-free control of spin and charge degrees of freedom in carbon-based nanostructures, paving the way for low-power spintronic devices.

This study investigates the phase evolution and magnetic properties of YMn 0.5 Fe 0.5 O 3 near its morphotropic phase boundary, with a specific focus on the role of reaction kinetics modified by pre-sintering compaction. Experimental results indicate that eliminating macroscopic voids via pellet-pressing facilitates a more complete solid-state reaction. This process drives a partial structural transition from a metastable, geometrically frustrated layered hexagonal phase (P6 3 cm) to a three-dimensional orthorhombic phase (Pnma). 57 Fe Mössbauer spectroscopy reveals that the enhanced structural dimensionality allows iron ions to overcome the magnetic frustration associated with the initial large quadrupole splitting (1.20 mm/s), establishing a robust G-type antiferromagnetic order. Furthermore, macroscopic magnetic measurements demonstrate that the transition to the orthorhombic phase is accompanied by the emergence of weak ferromagnetism. This magnetic behavior originates from the cooperative tilting of MO 6 octahedra, which breaks local inversion symmetry and activates the antisymmetric Dzyaloshinskii-Moriya (D-M) interaction. Consequently, optimizing solid-state reaction conditions proves essential for tuning the spin-lattice coupling and magnetic ground states in complex multiferroic solid solutions.

One method of electric field control of magnetization is to generate a strain in a piezoelectric layer by applying an electric field to it and transfer this strain to a magnetostrictive nanoscale magnet or to the magnetostrictive soft layer of a magnetic tunnel junction deposited on the piezoelectric, thus controlling its magnetization state through inverse magnetostriction (Villari effect). Such strain-mediated electric field control of magnetization offers an extremely energy-efficient method of writing the magnetic state (∼100 aJ/bit). This review discusses the development of computing paradigms based on strain control of magnetism, termed “straintronics” or “magnetic straintronics,” and their future potential. Here, we discuss various Boolean memory and logic devices as well as non-Boolean and neuromorphic computing devices proposed and experimentally demonstrated along with their potential advantages and key challenges.

The discovery and control of intergrowth structures represent an important avenue for the targeted synthesis of new, more complex structure types. When including magnetic framework metal atoms, this enhanced complexity can transfer to rich magnetic ground states. Here, we show that the subtle adjustment of the composition of alkali-tellurium fluxes enables the synthesis of a new family of alkali chromium tellurides, A2.4 (A = Rb, Cs). Their ladder-like crystal structures integrate the 2D character of delafossite-like with the tunnel motifs of hollandite-like phases. This results in a previously unobserved unique hybrid framework. Direction-dependent magnetization measurements on oriented single crystals reveal distinct magnetic ground states: is antiferromagnetic with = 114.5 K, while is ferrimagnetic with = 125.0 K. This work underscores the simplicity and effectiveness of flux growth as a design strategy for discovering low-dimensionalmaterials.

2D layered materials provide a powerful platform for exploring the intertwined physics of magnetism, topology, and ferroelectricity. Here, using first-principles calculations, we reveal a rich landscape of tunable quantum phases and ferroelectric states in the 2D van der Waals material Ti3Se3Te2, controlled by magnetization orientation, stacking configuration, and interlayer sliding. For the monolayer, Ti3Se3Te2 is identified as a dynamically stable ferromagnet whose magnetization direction drives a phase transition between a trivial metal and a quantum anomalous Hall insulator with a nonzero Chern number. In bilayers, two distinct stacking configurations lead to markedly different behaviors: (i) the AA-stacking bilayer stabilizes an altermagnetic ordering and hosts a quantum spin Hall insulating phase characterized by a nonzero spin Chern number; and (ii) the AA'-stacking bilayer exhibits a three-state in-plane ferroelectricity, beyond the two-state out-of-plane ferroelectricity reported in many altermagnetic systems. Sliding-induced switching in this configuration reversibly modulates the in-plane polarization, the easy-magnetization axis, and the spin splitting. These results demonstrate that Ti3Se3Te2 integrates tunable topological phases, altermagnetism, and sliding-induced three-state in-plane ferroelectricity, establishing it as a versatile van der Waals platform for low-energy spintronic technologies, topological quantum science, and next-generation multifunctional applications.

Voltage-induced magnetization switching based on the voltage-controlled magnetic anisotropy (VCMA) effect is expected to be the ultimate low-power-consumption writing method for spintronic devices such as non-volatile magnetoresistive random-access memory. However, for conventional VCMA-driven dynamic magnetization switching, in which sub-nanosecond voltage pulses induce bidirectional switching by inducing a half precession of magnetization, even a small variation in the pulse widths of the order of several picoseconds can cause switching failure. This has become a major obstacle for developing voltage-controlled magnetoresistive random-access memory. Here we report VCMA-driven static magnetization switching by exploiting an artificial antiferromagnetic trilayer structure with interlayer exchange coupling. By applying bipolar voltages to the antiferromagnetic structure, we can demonstrate repeatable bidirectional switching. Unlike conventional dynamic switching, VCMA-driven static magnetization switching is induced in a wide range of pulse widths. This unconventional writing method is expected to be a key for developing various ultralow-power spintronic devices.

Abstract We investigate the dynamic magnetic response of planar ferromagnetic nanostructures with wire-ring morphology using micromagnetic simulations. By systematically varying the inner ring diameter and thickness, we analyze how geometric confinement governs the accessibility of stable and metastable magnetic states and shapes the spin-wave spectra. The equilibrium configurations are found to depend strongly on the relaxation pathway, giving rise to bistability for intermediate ring diameters. Dynamic susceptibility calculations under microwave excitation reveal distinct resonance spectra associated with low- and high-energy magnetic states, which we classify in terms of two energy-evolution paths. Spatial Fourier analysis of the out-of-plane magnetization identifies wire-like, ring-localized, and hybrid spin-wave modes, whose localization and spectral complexity are controlled by geometry. Our results demonstrate that planar wire-ring nanostructures offer a versatile platform for tailoring spin-wave excitations through geometric design, with potential implications for reconfigurable magnonic and spintronic devices.

Materials that intrinsically possess both magnetism and topological states represent a key frontier of quantum materials research. Recently, Mn2(Bi/Sb)2Te5has emerged as a promising candidate for hosting topological surface states coupled with intrinsic magnetic order, making it a potential magnetic Weyl semimetal. In this study, we investigate the magnetic and transport properties of Mn2Sb2Te5single crystals. The magnetization measurements reveal a spin glass state with field-induced ferromagnetism. Although heat capacity measurement indicates the absence of long-range order, the intrinsic magnetization in Mn2Sb2Te5significantly affects its electrical properties, as demonstrated by the anomalous Hall effect. This work provides valuable insights into the magnetism and the electronic properties of Mn2Sb2Te5, establishing Mn2(Bi/Sb)2Te5system as a compelling platform for exploring the interplay between magnetism and non-trivial band topology, enabling emergent quantum phases and novel transport responses not accessible in non-magnetic systems.