Stability studies of exchange bias field of Mn80Ir20/Co60Fe20B20 by network analyzer ferromagnetic resonance

The stability of the exchange bias field H-eb has been studied for Mn80Ir20/Co60Fe20B20 thin films by means of network analyzer ferromagnetic resonance. The results demonstrated that H-eb decreases with increasing temperature. The observed variation in the magnitude of H-eb and even a reversal in the sign of H-eb as a function of time above room temperature can be interpreted by a thermally activated reversal of antiferromagnetic domains as evidenced by the linear dependence of H-eb on ln t according to the Neel-Arrhenius law. Moreover, the correlation between the reversal of antiferromagnetic domains and the antiferromagnetic grain volume is obtained. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3491844]