Spin angular momentum transfer in a current-perpendicular spin-valve nanomagnet

Jonathan Z. Sun; T. S. Kuan; J. A. Katine; Roger H. Koch

doi:10.1117/12.521195

6 July 2004 Spin angular momentum transfer in a current-perpendicular spin-valve nanomagnet

Jonathan Z. Sun, T. S. Kuan, J. A. Katine, Roger H. Koch

Proceedings Volume 5359, Quantum Sensing and Nanophotonic Devices; (2004) https://doi.org/10.1117/12.521195
Event: Integrated Optoelectronic Devices 2004, 2004, San Jose, CA, United States

Abstract

Spin-angular momentum transfer (or spin-transfer for short) describes the angular momentum exchange between a spin-polarized current and a ferromagnetic conductor. When the conductor dimensions are reduced to around 100nm or below, the spin-angular momentum transfer effect becomes significant compared to the current-induced magnetic field. This paper describes some recent spin-transfer experimental findings in sub-100nm current-perpendicular spin-valve systems consisting of Co-Cu-Co nanopillars. The spin-transfer current is shown to cause a magnetic reversal of the thinner magnetic layer inside the nanopillar. The reversal is experimentally shown to reach sub-nanosecond speed. The effect of spin-transfer is best understood in terms of its modification to the effective Landau-Lifshiz-Gilbert damping coefficient, either increasing or decreasing its value depending on the direction and magnitude of the spin-polarized current. For sufficiently large spin-current, the net damping coefficient may change sign, resulting in amplification of magnetic precession, leading to a magnetic reversal. At finite temperatures, the effect of spin-transfer is to either increase or decrease the thermal agitation of the nanomagnet. A quantitative model is developed that adequately describes the finite temperature experimental observations of the dynamic spin-transfer effect.

Citation Download Citation

Jonathan Z. Sun, T. S. Kuan, J. A. Katine, and Roger H. Koch "Spin angular momentum transfer in a current-perpendicular spin-valve nanomagnet", Proc. SPIE 5359, Quantum Sensing and Nanophotonic Devices, (6 July 2004); https://doi.org/10.1117/12.521195

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