Current-Driven Magnetoresistance Oscillations in Asymmetric Spin Valves

M. Gmitra a and J. Barnaś b a Department of Theoretical Physics and Astrophysics, P.J. Šafárik University, Park Angelinum 9, 040 01 KoŠice, Slovak Republic and Institute for Theoretical Physics, University of Regensburg 93040 Regensburg, Germany b Department of Physics, Adam Mickiewicz University Umultowska 85, 61-614 Poznań, Poland and Institute of Molecular Physics, Polish Academy of Sciences Smoluchowskiego 17, 60-179 Poznań, Poland

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Received: 4 07 2007;

Within the macroscopic model we have calculated spin-transfer torque in asymmetric spin valves in the diffusive transport limit.Such systems exhibit a non-standard angular dependence of the torque, which leads to current-induced precessional modes at zero external magnetic field. We have found that the frequency of magnetoresistance oscillations exhibits hysteretic behavior when the system is driven between two steady precessional regimes. A finite temperature can suppress the irreversibility and give rise to bistable regime where, both the precessional regimes coexist.

DOI: 10.12693/APhysPolA.112.1267 PACS numbers: 75.60.Ch, 75.70.Cn, 75.70.Pa