Study of the resonance modes of a magnetic tunnel junction-like system

Abstract

The ferromagnetic resonance FMR modes of a magnetic tunnel junction-like system are investigated. Such a system consists of an interfacial F/AF interaction described by an exchange anisotropy field HE and a magnetic coupling of two ferromagnetic layers separated by a nonmagnetic interlayer. The latter interaction is accounted for by bilinear J1 and biquadratic J2 coupling strengths. The dispersion relation, the resonant frequency, f , as well as the corresponding mode intensity, I, versus applied field H curves, have been studied. Analytical formulas for the resonance condition and intensity have been derived for the low magnetic coupling/ high exchange anisotropy case. In this situation, the system is found to behave as two uncoupled layers with magnetic characteristics different from those of the initial layers; the effect of the low coupling is to modify the different anisotropies: J1 contributes to the exchange anisotropy while J2 modifies the magnetocrystalline anisotropies. For very strong coupling, the system behaves as a single F/AF system with effective exchange and magnetocrystalline anisotropy fields; these fields have been derived as a function of the individual layer magnetic parameters.