Controlling spin current polarization through non-collinear antiferromagnetism.

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.

Effect of (1 1 1)-oriented strain on the structure and magnetic properties of La0.7Sr0.3MnO3 thin films.

Using strain, i.e. subtle changes in lattice constant in a thin film induced by the underlying substrate, opens up intriguing new ways to control material properties. We present a study of the effects of strain on structural and ferromagnetic properties of (1 1 1)pc-oriented La0.7Sr0.3MnO3 epitaxial thin films grown on NdGaO3, SrTiO3, and DyScO3 substrates. (The subscript pc denotes the pseudo-cubic symmetry.) The results show that La0.7Sr0.3MnO3 assumes a monoclinic unit cell on NdGaO3 and DyScO3 and a rhombohedral unit cell on SrTiO3. For La0.7Sr0.3MnO3 on NdGaO3 and DyScO3 a uniaxial magnetic anisotropy is found, while La0.7Sr0.3MnO3 on SrTiO3 is magnetically isotropic. The Néel model is used to explain the anisotropy of the thin films on NdGaO3 and SrTiO3, however, for La0.7Sr0.3MnO3 on DyScO3 the effect of octahedral rotations needs to be included through the single ion model. Through examination of the Curie temperature of the strained films we suggest that (1 1 1)-strain has a different effect on the Jahn-Teller splitting of e g and t 2g electron levels than what is seen in (0 0 1)pc-oriented La0.7Sr0.3MnO3 thin films.