Spin-flip noise due to nonequilibrium spin accumulation

Abstract

When current flows through a magnetic tunnel junction (MTJ), there is spin accumulation at the electrode-barrier interfaces if the magnetic moments of the two ferromagnetic electrodes are not aligned. Here we report that such nonequilibrium spin accumulation generates its own characteristic low frequency noise (LFN). Past work viewed the LFN in MTJs as an equilibrium effect arising from resistance fluctuations ($S_R$) which a passively applied current ($I$) converts to measurable voltage fluctuations ($S_V=I^2{S}_R$). We treat the LFN associated with spin accumulation as a nonequilibrium effect, and find that the noise power can be fitted in terms of the spin-polarized current by $S_{I}f=aI\coth (\frac{I}{b})-ab$, resembling the form of the shot noise for a tunnel junction, but with current now taking the role of the bias voltage, and spin-flip probability taking the role of tunneling probability.

6 pages, 5 figures

References in corpus (7)

• Large magnetoresistance in bcc Co/MgO/Co and FeCo/MgO/FeCo tunneling junctions
• Shot Noise Induced by Nonequilibrium Spin Accumulation
• Sub-Poissonian shot noise in CoFeB/MgO/CoFeB-based magnetic tunneling junctions
• Band edge noise spectroscopy of a magnetic tunnel junction
• Symmetry-dependent electron-electron interaction in coherent tunnel junctions resolved by zero bias anomaly measurements
• Low frequency noise characteristics of sub-micron magnetic tunnel junctions
• Low frequency noise peak near magnon emission energy in magnetic tunnel junctions