Spin Manipulation in van der Waals Ferromagnets and Antiferromagnets

van der Waals materials have a number of properties that make them intriguing for spintronic devices. They can be thinned to the two-dimensional limit while maintaining good magnetic properties, they can manifest a many different magnetic states and a wide range of resistivities, and they can be incorporated into heterostructures with pristine interfaces and large magnetoresistance. Here, I will discuss several experiments designed to understand and enable control of the spin dynamics in these materials.

Our research group has developed techniques to integrate insulating vdW ferromagnets with layers of heavy metals or topological insulators. With the heavy metals we demonstrate efficient transmission of spin currents to generate spin-orbit torque on the vdW magnet. With the topological insulators we show that an insulating magnet can induce an anomalous Hall effect whose amplitude can be tuned by gate voltage with a strong peak near the Dirac point. This is the signature expected due to Berry curvature associated with an exchange gap in the topological surface states.

We are also investigating the spin-dynamics in the layered antiferromagnet CrSBr, which has biaxial magnetic anisotropy with an easy axis in-plane. Depending on the angle and magnitude of applied magnetic field, this anisotropy allows for a variety of states (antiparallel spin sublattices, spin-flop, and spin-flip), each with distinct behavior for the pair of antiferromagnetic resonances. We have characterized these modes using resonance measurements are exploring whether they can be addressed individually and excited by spin-orbit torque.