Current-driven magnetic excitations in Permalloy based multilayer nanopillars
Abstract
We used a Ni_84Fe_16 ferromagnetic alloy with low magnetic anisotropy for studies of current-driven magnetization reversal in magnetic nanopillars at room temperature and 4.2 K. At both temperatures, the current-driven switching gives hysteretic steps in differential resistance measurements at small applied field H, and a reversible switching peak at large H. In the reversible switching regime, we also separately identify the features associated with magnetic excitations. We show that the reversible switching peak is due to random telegraph noise switching of the nanopillar magnetization. The dependence of the telegraph noise on temperature is inconsistent with a macrospin version of the spin-torque model. Instead, we describe the current-driven excitation and switching in terms of a current-dependent magnetic temperature that can differ substantially from the phonon temperature. If time permits, we will show how the effective temperature model explains the data for magnetically coupled Co/Cu/Co samples. This work was done in collaboration with J.Bass, W.P. Pratt Jr., N.O. Birge, H. Kurt, and R.Loloee, and supported by MSU CFMR, CSM, the MSU Keck Microfabrication facility, the NSF through Grants DMR 02-02476, 98-09688, and 00-98803, and Seagate Technology.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MAR.H1003U