Temperature dependence of interlayer exchange coupling and Gilbert damping in synthetic antiferromagnetic trilayers investigated using broadband ferromagnetic resonance

Abstract

This work reports a comprehensive investigation of the temperature dependence of the interlayer exchange coupling in the antiferromagnetic coupling of a FeNi/Ru/FeNi trilayer sample using broadband ferromagnetic resonance. The temperature dependence of the interlayer exchange coupling fields is obtained by applying Kittel fitting to the systematic frequency dependence of the resonance field between the acoustic and optic modes and by assuming equal effective magnetization of the two resonance modes. It is found that the value of the exchange coupling field increases with decreasing temperature, showing excellent agreement with the existing theories regarding the spacer and interface and the thermal excitations of the spin wave contributions to the temperature dependence. Additionally, the temperature dependence of the Gilbert damping coefficient was investigated for the acoustic and optic modes, where the optic mode damping coefficient was markedly different from and greater than of the acoustic mode. These results provide important information that will be helpful in the understanding of antiferromagnetic resonance.