Shixun Cao

Topological materials that simultaneously host robust high‐temperature skyrmions and nontrivial electronic band structures have attracted tremendous interest owing to their distinctive advantages for both fundamental research and prospective technological applications. Here, we report the observation of robust skyrmions in the Dirac kagome magnet Fe ₃ Ge, which exhibits a high Curie temperature of ∼ 650 K. At room temperature, Fe ₃ Ge shows a large intrinsic anomalous Hall conductivity of ∼ 380 Ω ⁻¹ cm ⁻¹ , originating from its nontrivial electronic band topology. Systematic magnetization measurements reveal a spin reorientation transition at ∼ 375 K, indicating a crossover from easy‐plane to easy‐axis magnetic anisotropy. Below the spin reorientation temperature, a large topological Hall effect is observed, arising from microscopic noncoplanar spin structures. Lorentz transmission electron microscopy shows that mesoscopic skyrmions are stabilized in the easy‐axis magnetic anisotropy regime and persist over an exceptionally wide temperature window of 375–650 K, far exceeding that of most previously reported skyrmion‐hosting materials. These results establish Fe ₃ Ge as a promising platform for exploring diverse topological properties, with strong potential for advancing future high‐temperature spintronic applications, ranging from next‐generation information storage to logic computing devices.

In rare-earth orthoferrites (RFeO3), the R3+-Fe3+ exchange interaction plays a crucial role in modulating the magnetic properties of single crystals. Here, we report the effect of Tb3+ substitution on spin switching in an Er0.9Tb0.1FeO3 single crystal. Along the a-axis, Type-II spin switching (SSW-II) is observed under zero-field-cooling warming (ZFC) mode, while multi-step SSW-II occur under field-cooled cooling (FCC) mode. These behaviors are absent in the parent ErFeO3 and TbFeO3 single crystals. Both SSW-II processes are highly sensitive to external fields and can be tuned by magnetic fields below 50 Oe. These two SSW phenomena are attributed to the flipping of the Tb3+ sublattice moment, which is driven by the Tb3+-Fe3+ exchange interaction. We further find that the critical field Hc for the field-induced spin switching reaches a maximum value of 463 Oe at 15.5 K. Compared with parent ErFeO3, 10% Tb3+ substitution reduces the maximum Hc by 84.57% owing to a weakened Er3+-Fe3+ interaction and the consequent suppression of magnetic pinning between the Fe3+ and Er3+ sublattices. These results demonstrate that the competition between (Er3+, Tb3+)-4f and Fe3+-3d electrons in Er0.9Tb0.1FeO3 gives rise to spin switching that is highly tunable by low magnetic fields and temperature, making this material a promising candidate for low-power spintronic devices.

Antiferromagnets, capable of hosting terahertz (THz)-frequency spin waves, are promising candidates for ultrafast, low-dissipation information processing. However, the systematic control of spin modes in antiferromagnetic orthoferrites remains relatively scarce. Here, we demonstrate the emission and detection of narrowband sub-THz radiation from quasi-ferromagnetic (q-FM) and quasi-antiferromagnetic (q-AFM) modes in ErxTm1−xFeO3 (x = 0, 0.5, and 1) single crystals. By varying the angle θ between the incident THz magnetic field (HTHz) and the c-axis, we can selectively excite either the q-AFM or q-FM mode and modulate their amplitude and relaxation dynamics. Furthermore, we show that the resonant THz frequencies in b-cut crystals are remarkably robust, exhibiting dependence on temperature and external magnetic fields (HDC). We calculated the magnetic anisotropy constants based on the temperature dependence of the spin waves. Finally, we generate narrowband THz emission via the inverse magneto-refraction effect by optically exciting q-AFM spin resonances.

ZrB12 has been suggested as a multicomponent superconductor exhibiting unconventional features, including characteristics of both type-I and type-II superconductivity, yet the multiband nature of ZrB12 still remain controversial. Here, a ZrB12 micro-bridge was fabricated by focused ion beam technique. The self-field critical current density (Js) is directly derived from the electrical transport measurements. It is found that the temperature dependence of (Js) can be well fitted by considering the two-band s-wave symmetry, thus, providing direct transport evidence for two-band superconductivity in ZrB12 and support its multicomponent nature. The observed crossover behavior further suggests a possible connection between multiband coupling and the previously reported coexistence of type-I and type-II superconducting characteristics, offering new insight into the superconducting mechanism in dodecaborides.

Low-energy antiferromagnetic phase transitions offer an appealing platform for low-power spintronic functionalities, yet their direct electrical access in insulating antiferromagnets remains challenging, particularly in the low-field regime where subtle Neeel vector reorientations dominate. Here, we demonstrate that targeted rare-earth-site engineering enables an electrically accessible metamagnetic transition in the insulating orthoferrite Ho0.5Dy0.5FeO3. By combining the distinct spin-reorientation sequences of DyFeO3 and HoFeO3, Dy substitution stabilizes a dual spin-reorientation pathway, hosting an intermediate state with a reduced energy barrier. This low-energy antiferromagnetic state can be tuned into the weak-ferromagnetic state under low magnetic fields. The critical field decreases with increasing temperature, providing a favorable window for functional manipulation. Both longitudinal and transverse spin Hall magnetoresistance channels exhibit clear and reproducible signatures of the metamagnetic transitions. Owing to the enhanced sensitivity of the transverse channel, additional low-field features are resolved, reflecting the projection of the Neel vector onto the spin-accumulation direction. Electrical transport measurements correlate directly with the magnetically determined phase boundaries, establishing a purely electrical access to low-energy phase transitions and to illustrate a viable pathway for exploring low-power spin dynamics in insulating oxide antiferromagnets.