Antiferromagnetic spintronics offers a compelling route toward high-density, ultrafast, and field-insensitive nanoscale devices, yet realizing electrically controllable magnetic textures at room temperature remains challenging. Existing approaches rely on extrinsic skyrmion textures or interfacial Dzyaloshinskii-Moriya interactions, lacking ground-state stability. Although Fe-doped Mn3Sn has demonstrated 6-spin-exchange-driven non-coplanar order, the resulting topological Hall effect vanishes above ~150 K, precluding room-temperature operation. Here we report Mn2.7Co0.3Sn single crystals in which Co substitution stabilizes an intrinsic non-coplanar spin texture persisting above 300 K. Neutron diffraction reveals a 10° spin canting and finite scalar spin chirality at 300 K, generating a topological Hall resistivity of 0.49 μΩ·cm. First-principles calculations confirm the real-space Berry-curvature origin from scalar spin chirality, distinct from the spin-orbit-coupling-dependent momentum-space mechanism. The distinct 3d7 electron count of Co, relative to Fe (3d6), correlates with enhanced thermal stability, demonstrating that substituent-specific electronic structure modulates the exchange landscape beyond generic electron doping. Furthermore, the topological response exhibits bond-directional strain sensitivity: c-axis compression preserves kagome symmetry and modulates the 6-spin strength, whereas ab-plane compression breaks trigonal symmetry. These findings establish substitutional chemistry as a route toward room-temperature topological antiferromagnetic devices.
Materials that transition between metal and insulator, the two main states that distinguish all solids, are fascinating because they underlie many mysteries at the frontier of solid-state physics. In 1T-TaS2, the metal-insulator transition is linked to a metastable hidden state arising within a chiral charge density wave (CDW) whose basic nature remains an open question. In this work, we show that pulses of current through this material create current-carrying filamentary channels that distinguish the ‘metallic’ hidden state and the ‘insulating’ CDW states. These channels have remained undetected in previous measurements and yet are directly linked to the properties of the hidden state. We leverage the metastability of these conduction channels to demonstrate electrical control of their creation, erasure and location. Our findings show that physical elements such as boundaries and interfaces play a key role in the properties of the hidden state characterizing the metal-insulator transition. We propose new possibilities for in-situ electrical design of reconfigurable conductive networks, highlighting the broader device potential of these metastable states.
Abstract Spin-orbit coupling locks spin direction and spatial orientation and generates, in semi-classical magnets, a local spin easy-axis and associated ordering. Quantum spin-1/2’s defy this fate: rather than spins becoming locally anisotropic, the spin-spin interactions do. Consequently interactions become dependent on the spatial orientation of bonds between spins, prime theoretical examples of which are Kitaev magnets. Bond-directional interactions imply the existence of bond-directional magnetic modes, spin excitations that render crystallographically equivalent bonds magnetically inequivalent, which yet have remained elusive experimentally. Here we show that resonant inelastic X-ray scattering allows us to explicitly probe the bond-directional character of magnetic excitations. To do so, we use a scattering plane spanned by one bond and the corresponding spin component and scan a range of momentum transfer that encompasses multiple Brillouin zones. Applying this approach to Na 2 IrO 3 we establish the different bond-directional characters of magnetic excitations at ~10 meV and ~45 meV. The bond-directional nearest-neighbor excitations are a fingerprint of the dominant Kitaev interactions and even prevail in the magnetically ordered state.
The A-site layered double perovskite RBaFe2O6 (R = Pr, Nd, Sm) containing the unusually high-valent Fe3.5+ state exhibits a cascade of charge-disproportionation (CD) transitions on cooling driven by competing electronic instabilities: 2Fe3.5+ → Fe3+ + Fe4+ → 1.5Fe3+ + 0.5Fe5+. Using neutron powder diffraction and magnetisation measurements, we determine the evolution of magnetic structures across these successive CD regimes. NdBaFe2O6 and SmBaFe2O6 exhibit two successive spin reorientation transitions, with the ordered moments reorienting between crystallographic directions before stabilising in a low-temperature multi-k (Γ + Y) magnetic state. In contrast, PrBaFe2O6 undergoes a direct spin reorientation without an intermediate phase, while a weak Y component is already present near the ordering temperature. These results show that the magnetic evolution closely follows the CD progression and is consistent with changes in exchange topology and magnetocrystalline anisotropy, leading to spin reorientation and multi-k magnetism. RBaFe2O6 thus provides a model system in which charge redistribution directly controls complex magnetic order in high-valent Fe oxides.
Abstract We find the extrinsic anomalous Hall conductivity (AHC) to be comparable to the intrinsic one in roughly half of the altermagnetic spin Laue groups in the limit of large exchange splitting. In materials with a finite Dzyaloshinskii-Moriya type interaction, the extrinsic contribution is essential even in the clean limit. In other altermagnets it is mostly negligible. This peculiar behavior is linked to the nonanalytic dependence of the intrinsic AHC on spin-orbit coupling. Both originate from the lifting of the spin degeneracy along the nodal planes as the weak spin-orbit coupling breaks the nonrelativistic spin symmetry.
