Thermal stability of the antiferromagnetically coupled Co/Cu/Co stack

The long-term thermal stability of the hard artificial antiferromagnetic subsystem found in giant magnetoresistance and tunnel magnetoresistance sensors has been investigated at 182, 210, 240, and 300 degreesC using magnetoresistive and vibrating sample magnetometry measurements. The observed changes in the magnetoresistance signal and the saturation field show two processes, where the slower one has an activation energy of 1.5 +/-0.1 eV while the faster one occurs too fast to fit accurately. In order to probe the stability of the Co/Cu interface, nonlinear (magneto-optical magnetization-induced second-harmonic generation) measurements were done which reveal a dramatic enhancement of the second harmonic tensor components, also dominated by two time constants. (C) 2001 American Institute of Physics.