Interlayer Coupling and Magnetization Process in Co/Pt/Gd/Pt Multilayers

We investigated the magnetization process in Co/Pt/Gd/Pt multilayer films in order to study the indirect exchange coupling between Co and Gd through Pt. Normal spin-flop behavior was observed in samples with a Pt layer thickness tpt≪10Ã…. On the other hand, a novel hysteresis loop with "negative coercivity" was observed for tPt≫10Ã…. This loop is considered to be due to the combined effect of the antiferromagnetic coupling between the Co and Gd layers, and the large magnetic anisotropy acting on the Co layer magnetization. The calculated magnetization curves agree well with experimental results. The antiferromagnetic coupling strength estimated from a comparison of calculations and experiment decays in an oscillating manner with increasing tPt.