The ability to efficiently control topological magnetism is crucial for advancing technological applications and deepening our understanding of magnetic systems. Although emerging van der Waals (vdW) multiferroics present a promising frontier for energy-efficient spin manipulation, the control of topological magnetism remains challenging due to its scarcity in multiferroics. Here, we demonstrate that highly tunable merons and antimerons emerge in monolayer multiferroic CuCrP₂S₆ (CCPS). The antiferroelectric-to-ferroelectric (AFE-FE) transition enhances exchange couplings, notably reducing meron density and increasing meron size during cooling. Merons exhibit unique dynamics, characterized by nontrivial attraction and annihilation processes, which generates distinct long-lived spin waves and reduces meron number difference between AFE and FE phases until they vanish. Importantly, ultrafast laser pulses can induce ferroelectricity-tunable merons from a uniform in-plane magnetization, re-leading to a large difference in meron density between the AFE and FE phases. These findings enhance our understanding of topological magnetism and open up exciting avenues for controlling the properties and dynamics of topological states through electrical and optical methods.

The effective manipulation of perpendicular magnetization through spin-orbit torque (SOT) holds great promise for magnetic memory and spin-logic device. However, field-free SOT switching of perpendicular magnetization remains a challenge for conventional materials with high symmetry. This study elucidates a full electrical manipulation of the perpendicular magnetization in an epitaxial [111]-orientated Pt/Co heterostructure. A large anisotropic epitaxial strain induces a symmetry transition from the ideal C3v to C1v, attributed to the mismatch between [112] and [110] directions. The anisotropic strain also generates a noteworthy in-plane magnetization component along the [112] direction, further breaking magnetic symmetry. Notably, the high-temperature performance under 393 K highlights the robustness of strain-induced in-plane symmetry breaking. Furthermore, eight Boolean logic operations have been demonstrated within a single SOT device. This research presents a method for harnessing epitaxial strain to break in-plane symmetry, which may open a new avenue in practical SOT devices.

Explicit interactions, e.g., dipolar and exchange couplings, usually govern magnetization dynamics. Some interactions may be hidden from the global crystal symmetry. We report that in a large class of uniaxial antiferromagnets, a hidden Dzyaloshinskii-Moriya interaction with retaining global inversion symmetry quenches the spin of the magnon along the Néel vector n, thus forbidding its angular-momentum flow. Some magnon spins, termed "nodal"and "corner"spins, survive when they distribute singularly at the hot spots, i.e., high-symmetric degeneracy points in the Brillouin zone, and are protected by crystal symmetries. The biased magnetic field along n broadens such distributions, allowing bulk spin transport with unique signatures in the magnetic field and temperature dependencies. This explains recent experiments and highlights the role of hidden interaction.

As a material platform for spintronics, ferrimagnets have garnered considerable attention because of their unique behavior. Recently, interlayer Dzyaloshinskii-Moriya interaction (DMI) has significantly heightened interest in its ability to design three-dimensional long-range chiral spin textures, thereby promising enhancements in the performance of magnetic random-access memory devices. To date, experimental reports primarily focused on the observation of interlayer DMI and its field-free switching capability, while systematic investigations into the temperature dependence of interlayer DMI in ferrimagnetic systems are lacking. Here, we experimentally observe a record-high interlayer DMI effective field and demonstrate the strongly temperature-dependent interlayer DMI strength within a trilayer system incorporating the ferrimagnet TbFe. Our results show that temperature can significantly manipulate the strength of interlayer DMI in trilayer structures composed of a ferrimagnetic rare-earth and transitionmetal alloy, consistent with first-principles calculations. These insights herald an effective methodology to modulate the strength of interlayer DMI, offering significant advantages for the prospective development of semiconductor devices based on interlayer DMI.

As a critical component of high-efficiency and low-power memory devices, the development of magnetic tunnel junctions (MTJs) with large tunneling magnetoresistance (TMR) is highly demanded. Altermagnets, a particular magnetic system, with zero net magnetizations and non-spin-degenerate conductance due to momentum-dependent spin polarization, can generate TMR when used to replace ferromagnetic and traditional antiferromagnetic electrodes. In this study, we present a ferromagnet/insulator barrier/altermagnet junction that exhibits large intrinsic TMR. In this system, the ferromagnetic electrode is a half-metallic alloy with a unidirectional Fermi surface. We demonstrate that a large TMR can be obtained in V<inf>0.5</inf>Cr<inf>0.5</inf>O<inf>2</inf>/TiO<inf>2</inf>/RuO<inf>2</inf> through first-principles calculations and quantum transport calculations. However, the TMR ratio is almost zero when the ferromagnetic electrode is replaced with pristine VO<inf>2</inf> or CrO<inf>2</inf>. This behavior can be attributed to the unidirectional conduction channel rather than transport direction. Our work presents an efficient approach to realize large TMR ratio in ferromagnet/insulator barrier/altermagnet MTJs, which could contribute to the potential development of altermagnet-based spintronic devices.

Two-dimensional van der Waals (vdW) ferromagnetic/semiconductor heterojunctions provide an ideal platform for studying and exploiting tunneling magnetoresistance (TMR) effects, due to the versatile band structure of semiconductors and high quality of their interfaces. In all-vdW magnetic tunnel junction (MTJ) devices, both the magnitude and sign of TMR can be tuned by an applied voltage. Typically, as the bias voltage increases, the amplitude of TMR initially decreases, followed by a reversal and/or oscillation in its sign. Herein, we report on an unconventional bias-dependent TMR observed in all-vdW Fe<inf>3</inf>GaTe<inf>2</inf>/GaSe/Fe<inf>3</inf>GaTe<inf>2</inf> MTJs, where TMR first increases, then decreases, and ultimately undergoes a sign reversal as the bias voltage increases. By considering the coherent degree of in-plane electron momentum k∥ and the decay of the electron wave function through the semiconductor spacer layer, our theoretical prediction successfully explains this unconventional bias-dependent TMR. Consequently, our results offer a deeper understanding of bias-dependent spin-transport in semiconductor-based MTJs and provide new insights into semiconductor spintronics.

Details on anisotropic magnon dispersion in van der Waals (vdW) ferromagnetic insulators CrPS4 and CrSBr are reported, driven by anisotropic Heisenberg exchange couplings arising from in-plane broken crystal symmetry. The anisotropic magnon dispersion contributes to longitudinal and transverse magnon currents generating the anisotropic spin Seebeck effect (ASSE) and the thermal Hall effect (THE) accompanied with spin Nernst effect (SNE), requiring neither external magnetic field nor Berry curvature. In CrPS4, the ASSE exhibits a very large anisotropy ratio of over 100% as the thermal gradient along different main axes, and this ratio can be further tuned by temperature or a gate current. The THE and SNE unconstrained by spin-orbit coupling (SOC) emerge when the thermal gradient is not parallel to the main axis, characterized by a large Hall angle approximate to 0.4. Compared to CrPS4, CrSBr exhibits a more limited anisotropic magnon transport owing to the less variation in magnon group velocities along different main axes. Moreover, the reversed magnitude relationship of magnon group velocities leads to the transverse magnon current being oriented in the opposite direction. These findings identify low-symmetry vdW magnetic materials as a promising framework for generation and manipulation of anisotropic magnon transport, relevant for spincaloritronic devices in the ultrathin regime.