Electrical Measurement of Thermally Driven Spin Hall Voltage in Platinum with Permalloy contacts

A group of effects coupling spin current with heat has drawn considerable attention due to their large potential for applications in spincaloritronics[1]. Recently, a new member of the family which converts thermal gradient into pure spin current in nonmagnetic conductors, named the spin Nernst effect, was observed. Here, we report a surprisingly large magnetic-field dependent voltage (<800 nV) across two permalloy contacts on a platinum channel patterned into a cross shape, while in the orthogonal channel, electrical current is utilized to create local thermal gradient by Joule heating. From finite element analysis as well as local electrical transport thermometry measurements, we estimate thermal gradients to be 1.5 K/micron near the permalloy contacts at electrical current of 10 mA. We will further discuss the origins of the large observed voltage by presenting several experimental results which we strongly feel rules out any unintended electrical effects such as spin Hall effect.
[1] G. E. W. Bauer et al., Nat. Mat., 11, 391 (2012).