The interconversion of charge and spin currents via spin-Hall effect is essential for spintronics. Energy-efficient and deterministic switching of magnetization can be achieved when spin polarizations of these spin currents are collinear with the magnetization. However, symmetry conditions generally restrict spin polarizations to be orthogonal to both the charge and spin flows. Spin polarizations can deviate from such direction in nonmagnetic materials only when the crystalline symmetry is reduced. Here, we show control of the spin polarization direction by using a non-collinear antiferromagnet Mn₃GaN, in which the triangular spin structure creates a low magnetic symmetry while maintaining a high crystalline symmetry. We demonstrate that epitaxial Mn₃GaN/permalloy heterostructures can generate unconventional spin-orbit torques at room temperature corresponding to out-of-plane and Dresselhaus-like spin polarizations which are forbidden in any sample with two-fold rotational symmetry. Our results demonstrate an approach based on spin-structure design for controlling spin-orbit torque, enabling high-efficient antiferromagnetic spintronics.

A large enhancement of the thermoelectric figure of merit is reported in single‐crystalline films of CrN. The mechanism of the reduction of the lattice thermal conductivity in cubic CrN is similar to the resonant bonding in IV–VI compounds. Therefore, useful ideas from classic thermo­electrics can be applied to tune functionalities in transition metal nitrides and oxides.

We report the thermoelectric figure of merit of chromium nitride, CrN, and its optimization through hole-doping. CrN is a degenerate semiconductor with large thermoelectric power, reaching $-185\mu \text{V}/\text{K}$ at 420 K. The resistivity can be reduced through hole-doping in the series ${\text{Cr}}_{1-x}{\text{V}}_x\text{N}$ , keeping a large thermopower. The thermal conductivity of CrN is rather low compared to other transition-metal nitrides, reaching its minimum value of 1.0 W/m K at 267 K. The largest $ZT=0.04$ was measured for ${\text{Cr}}_{0.9}{\text{V}}_{0.1}\text{N}$ at room temperature. Our results suggest that CrN could be a good starting point for the design of a thermoelectric material with optimal mechanical properties.

Engineered heterostructures formed by complex oxide materials are a rich source of emergent phenomena and technological applications. In the quest for new functionality, a vastly unexplored avenue is interfacing oxide perovskites with materials having dissimilar crystallochemical properties. Here, we propose a unique class of heterointerfaces based on nitride antiperovskite and oxide perovskite materials as a previously unidentified direction for materials design. We demonstrate the fabrication of atomically sharp interfaces between nitride antiperovskite Mn₃GaN and oxide perovskites (La_0.3Sr_0.7)(Al_0.65Ta_0.35)O₃ and SrTiO₃. Using atomic-resolution imaging/spectroscopic techniques and first-principles calculations, we determine the atomic-scale structure, composition, and bonding at the interface. The epitaxial antiperovskite/perovskite heterointerface is mediated by a coherent interfacial monolayer that interpolates between the two antistructures. We anticipate our results to be an important step for the development of functional antiperovskite/perovskite heterostructures, combining their unique characteristics such as topological properties for ultralow-power applications.

CrN was doped with Mo and W to study the effect of heavy elements alloying on its thermoelectric properties. An spontaneous phase segregation into Mo- and W-rich regions was observed even at the lowest concentrations probed at this work $(\simeq 1\%)$ . In the particular case of W, this segregation creates nanoinclusions into the Cr_1–xW_xN matrix, which results in a substantial reduction of the thermal conductivity in the whole temperature range compared to undoped CrN. In addition, an increased hybridization of N:2p and 4d/5d orbitals with respect to Cr:3d decreases the electrical resistivity in lightly doped samples. This improves substantially the thermoelectric figure of merit with respect to the undoped compound, providing a pathway for further improvement of the thermoelectric performance of CrN.