Angular Dependence of Spin-Torque Critical Currents in CPP-GMR Read Heads
Abstract
This paper derives expressions for the critical current at the onset of spin-transfer-torque (STT) instability in CPP-GMR read heads, as a function of the relative angle (theta) between the free and reference layer magnetizations. Including a general angular dependent STT coefficient B(q=cos(theta)) exclusive of the angular momentum conserving sin(theta) factor, the critical current is found to depend on both B(q) and dB/dq in the non-collinear case |q| < 1. The paper also details the experimental measurement of the angular dependent critical currents on 50-nm sized CPP-GMR devices with synthetic antiferromagnet pinned layers, and fabricated using e-beam lithography. The measurements are consistent with prior theoretical models of the form B(q) ~ 1/[1+cnst*q], and indicate perhaps unanticipated implications for read head operation due to the critical current dependence on dB/dq.
Cite
@article{arxiv.cond-mat/0505117,
title = {Angular Dependence of Spin-Torque Critical Currents in CPP-GMR Read Heads},
author = {Neil Smith and J. . A. Katine and Jeffrey R. Childress and Matthew J. Carey},
journal= {arXiv preprint arXiv:cond-mat/0505117},
year = {2009}
}
Comments
6 pages, 8 figures. This work was presented as paper FB-04 at Intermag'05 (Nagoya, Japan), is presently accepted for publication, and should appear (in possibly revised form) with the Intermag'05 conference proceedings in the IEEE Transactions on Magnetics