Theory of oblique-field magnetoresistance from spin centers in three-terminal spintronic devices*

Spin and charge transport across magnetic/non-magnetic interfaces have sparked interest over the past several years. So-called three terminal measurements have been interpreted in two primary ways: either as a Hanle effect associated with spin transport into a non-magnetic material or as a magnetoresistance induced by spin-dependent transport through a defect situated at the interface [1-3].

We present a general stochastic Liouville theory of electrical transport across a barrier between two conductors that occurs via sequential hopping through a single defect's spin-0 to spin-1/2 transition. We find magnetoresistance features to the Hanle effect but in fact originate from Pauli blocking and not spin accumulation [4]. We also predict that evolution of the defect's spin modifies the conventional Hanle response, producing an inverted Hanle signal. Three terminal measurements with oblique magnetic fields [5] provide a means to delineate the two mechanisms. By comparing responses at different field angles, we can rule out effects of surface roughness induced magnetic fields on the response. Lastly, ramifications of the interfacial defects on non-local (four terminal) measurements are examined.

This work was done in collaboration with Michael E. Flatte.

[1] R. Jansen et al., Semicond. Sci. Technol. 27, 083001 (2012)
[2] Y. Song and H. Dery, Phys. Rev. Lett. 109, 047205 (2014)
[3] H. Inoue, et al., Phys. Rev. X 6, 041023 (2015)
[4] N. J. Harmon and M. E. Flatte arXiv:2008.05623
[5] S. He, et al., J. Appl. Phys. 119, 113902 (2016)