ASCENT Theme 2 Liaison Meeting/Spin-orbit torque and Nernst effects in Bi-Sb/ferromagnet heterostructures


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Spin-orbit torque and Nernst effects in Bi-Sb/ferromagnet heterostructures

Speaker: Niklas Roschewsky (UC Berkeley) from Prof. Sayeef Salahuddin's Group

Topological insulators have gained considerable interest recently due to their potential as spin current generators for room temperature memory applications. In this work, we show harmonic Hall measurements of spin-orbit torque (SOT) in MBE grown Bi-Sb/Co bilayers [1]. We find that signals in our samples show significant ordinary Nernst effect (ONE). This thermal effect can be a spurious signal in harmonic Hall measurements. 

We are proposing two control experiments to separate the ONE in Bi-Sb from SOT. First, we compare harmonic measurements in Bi-Sb/Co and Bi-Sb/Al. While SOT is absent in the sample without magnet, we still see large signals in the second harmonic Hall voltage due to the ONE. Second, we investigate the scaling of V2ω with external magnetic field Bext. While it is expected that SOT effects are suppressed at large magnetic fields, we find that the second harmonic voltage in Bi-Sb/Co scales linearly with the external field, as expected from the ONE. We believe that a careful consideration of these effects are needed to properly distinguish pure spin mediated effects. 

Related to task: 2776.021

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