Spin Fluctuations in Small Magnetic Tunnel Junctions*

Inelastic scattering of electrons by both phonons and magnons has been known to alter electronic transport through magnetic tunnel junctions (MTJs) [1]. More recently, spin-transfer torque driven thermal and even quantum fluctuations of the magnetic moments of the leads of small MTJs have been demonstrated to alter the magnetoresistance of the junction, leading to interesting nonlinear I-V behavior [2]. In this talk, I show how a simple model for spin-fluctuations of an MTJ gives rise to both inelastic charge transport and spin-transfer torque, taking both effects on equal footing. We qualitatively reproduce the electrical response of small MTJs, and show that inelastic charge transport dominates at low temperatures and biases, while spin-transfer torque is the dominant mechanism behind the nonlinear response at high temperatures and/or biases.

[1] S. Zhang, P. M. Levy, A. C. Marley, and S. S. P. Parkin, Physical review letters 79, 3744 (1997)
[2] J. Z. Sun and D. C. Ralph, Journal of Magnetism and Magnetic Materials 320, 1227 (2008); A. Zholud et al. arXiv:1703.09335 (2017)