Controlling Interfacial Magnetic Anisotropy and Spin-Orbit Torques with Insulating CdWO₄

We examine the effects of low crystal symmetry when metallic magnetic films are deposited on CdWO₄, a readily-available, insulating substrate with strong spin-orbit coupling whose symmetries can be restricted to a single mirror plane if cleaved with the b-axis in-plane. We show that magnetic thin films interfaced with CdWO₄ have strong magnetic anisotropy induced by the low-symmetry crystal structure. This anisotropy is strongly temperature-dependent, exceeding 200 Oe at low temperatures. In addition, measurements of spin-orbit torque in such bilayers exhibit torque components that are commensurate with the symmetry of CdWO₄. This suggests an interfacial torque mechanism in which spin-polarized electrons flowing within the magnetic layer and scattering from the insulating CdWO₄ can produce a spin-orbit torque acting back on the magnetic layer.