Spin dynamics and exchange interactions from a van der Waals antiferromagnet*

van der Waals (vdW) magnets provide unique opportunities to explore magnetic phenomena and spin dynamics down to the atomically-thin limit. Additionally, when paired with other vdW materials into 2D heterostructures, they can also enable new phenomena and functionalities arising from interfacial exchange interactions.

 

In this two-part talk, we will first present our recent progress in identifying the gigahertz antiferromagnetic resonances within the vdW antiferromagnet CrSBr with a significant triaxial magnetic anisotropy with the easy axis oriented within the vdW plane. [1]. This anisotropy modifies the form of the antiferromagnetic resonances and allows the excitation of different types of modes depending on the external field direction. We measure hybridized Left-handed and Right-handed chiral resonance modes when the magnetic field is applied parallel to the in-plane easy axis, in addition to the optical and acoustic modes when the field is applied perpendicular to the easy axis. We also achieve hybridization of the optical and acoustic modes through a rotation of the magnetic field away from the high symmetry axis.In addition, we will describe direct electrical detection of the antiferromagnetic resonance dynamics in few-layer CrSBr devices via their effect on tunnel magnetoresistance, and the effects of externally-applied spin-orbit torque on the mode damping. 

 

In the second part, we will show that exchange bias from CrSBr acting on the vdW ferromagnet Fe3GeTe2 induces a spatially non-uniform spin configuration through the thickness of the Fe3GeTe2 that is not readily achievable with conventional magnetic materials. We show that CrSBr exerts an in-plane exchange bias on the FGT, with a direction parallel to the in-plane anisotropy axis of the CrSBr.  This in-plane exchange bias provides  sufficient symmetry breaking needed to enable field-free spin-orbit-torque switching in Pt/Fe3GeTe2/CrSBr heterostructures [2]. Detailed temperature and thickness studies shows that a minimum thickness of the CrSBr layer of about 10 nm is required for a non-zero exchange bias at 30 K.