Phys. Rev. B 79, 094402 (2009) [6 pages]Experimental determination of spin-transfer torque nonadiabaticity parameter and spin polarization in permalloyReceived 27 June 2008; revised 8 December 2008; published 3 March 2009 The domain-wall depinning boundary, showing the variation in critical current density with magnetic field, is measured for notched permalloy wires using pulsed-current measurements. The structure of domain walls trapped at the pinning potential provided by the notch is imaged using photoemission electron microscopy. The experimental depinning boundary is compared with those obtained by micromagnetic simulations including the adiabatic and nonadiabatic spin-torque terms. This method allows for the determination of both the nonadiabaticity parameter β and spin current polarization P, which we obtain as β=0.040±0.005 and P=0.40±0.02 at room temperature. © 2009 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevB.79.094402
DOI:
10.1103/PhysRevB.79.094402
PACS:
75.60.Ch, 72.25.Ba, 72.25.Pn
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