ASCENT Theme 2 - Measurements of spin-orbit torque in advanced materials,including improvements in metrology

Measurements of spin-orbit torque in advanced materials,including improvements in metrology

Presenter: Prof. Dan Ralph (Cornell)

Date & Time: July 29, 4:00 pm eastern

Abstract:
This talk will cover recent progress in measurements of current-induced spin torques for magnetic memory devices. In collaboration with Darrell Schlom, my group has found that the collinear antiferromagnet RuO2 can generate a significant out-of-plane antidamping torque when the Neel vector is canted in between in-plane and out-of-plane configurations. This likely represents a new mechanism for generating current-induced spin-torque based not on spin-orbit interactions, but rather on a spin-split bandstructure occurring naturally in this collinear antiferromagnet. With Ramamoorthy Ramesh, we have also investigated spin-orbit torques in other oxide materials, finding that the quality of the interface between the spin-orbit material and the ferromagnet is critical in achieving efficient spin-orbit torques. As part of presenting these results, I will give some advice to avoid being tricked by artifacts when making measurements of current-induced torques in advanced materials. For magnetic layers with perpendicular magnetic anisotropy, we have developed an optical technique (Sagnac interferometry) which is sensitive enough to permit for the first time optical measurements of current-induced small-angle deflection from the out-of-plane orientation. The results of this technique demonstrate that the widely-used transport method for measuring spin-orbit torque for PMA samples, the second-harmonic Hall technique, is flawed for samples with significant planar Hall effects. For magnetic layers with in-plane magnetic anisotropy, we have developed a simple way to distinguish spin-pumping artifacts from measurements of spin-orbit torques.

This meeting is only available to the JUMP research community, such as Principal Investigators, Postdoc researchers, Students, and Industry/Government liaisons.