Vivek AMIN
Electrical control of magnetic order has widespread applications for information and communications technology. One “unconventional” scheme to manipulate magnetic order in layered devices is to generate a spin current in a magnetic layer that is absorbed by the same layer or by a nearby magnetic layer, causing a transfer of spin angular momentum or spin torque. In this talk, we discuss theoretical and experimental evidence of such unconventional spin torques in magnetic trilayers. These torques are unconventional in two ways: 1) the ferromagnetic layers are simultaneously the source and receiver of the spin torques, paving the way for single layer magnetic memories, and 2) spin torques on one ferromagnetic layer are modulated by the other ferromagnetic layer through interlayer scattering within a mean free path, resulting in torques that cannot be described by a spin diffusion model. The latter torques have a unique angular dependence given by ((E×z)·m2)m1, where E is the electric field, z points out-of-plane, and m1 and m2 are the magnetizations in the spin-orbit source and detector layer, respectively. To determine the qualitative behavior and quantitative dependence on material parameters, we present semiclassical and first principles transport calculations of spin currents and spin torques in magnetic trilayers containing ferromagnetic and/or antiferromagnetic layers. We study both intrinsic and extrinsic contributions to the spin torques to help disentangle the key physical mechanisms. Shedding light on the spin currents and spin torques generated within magnetic materials will help optimize the electrical control of magnetic order and could lead to exciting applications in information and communications technology.