Temperature-dependent biquadratic coupling in antiferromagnetically coupled Fe/FeSi multilayers

Fe/FeSi multilayers are known to exhibit a strong antiferromagnetic interlayer coupling peak centered at a nominal FeSi spacer thickness of {~}15±{}2 {} at room temperature, and to develop remanence in the magnetic hysteresis loop upon cooling to {~}100 K. An analysis of the hysteresis loops is found to require the inclusion of a temperature-dependent biquadratic (90^∘{} coupling) in addition to the bilinear coupling term in the energetics. The temperature dependence of the Fe/FeSi multilayer coupling can then be understood in terms that are applicable to conventional metallic multilayer systems such as Fe/Cr.