Time and Temperature Dependence of High Thermal Stability in NiO/Co/Cu/Co/M Spin Valves

Published

July 1, 1998

Author(s)

Robert D. McMichael, P J. Chen, William F. Egelhoff Jr.

Abstract

The thermal stability of Cu-Co 'bottom' spin valve structures deposited on NiO has been assessed as a function of temperature, time, and cap layer composition including Au, Ta and Ta_xO_y. Samples with 5.0 nm thick cap layers of Au showed a reduction in giant magnetoresistance (GMR) from 9.3% to 3.6% after a 0.5 hr anneals at 250 C. As a function of time, the sample resistance, R(t), showed an exponential saturation with a time constant, T, thich follows an Arrhenius law, T = To exp (δE/kT), with δE = 1.29 0.03 eV and To on the order of 10^-9 s. These parameters, which fit R(t), correlate with the time and anneal temperature dependence of GMR decay in the Au-capped spin valves. In contrast, samples with Ta or Ta_w O_y cap layers showed good stability for 0.5 hr anneals up to 325 C. Decreases in GMR from 12.7% to 3.9% following a 20 h anneal at 325 C are accompanied by significant changes in the hysteresis loops which appear to be associated with the pinned layer. With a 5.0 nm Ta cap, R(t) follows a logarithmic-like time dependence characteristic of a distribution of activation energies.

Citation

IEEE Transactions on Magnetics

Volume

34

Issue

No. 4

Pub Type

Journals

Keywords

anneal, spin valves, temperature dependence, thermal stability

Citation

McMichael, R. , Chen, P. and Egelhoff, W. (1998), Time and Temperature Dependence of High Thermal Stability in NiO/Co/Cu/Co/M Spin Valves, IEEE Transactions on Magnetics (Accessed October 17, 2025)