Exchange bias features in FeNi/FeMn/Gd-Co films

摘要

The exchange bias effect in FeNi/FeMn/Gd_xCo_(100-x) films with a pinning antiferromagnetic FeMn layer and an exchange-biased ferrimagnetic amorphous Gd-Co layer was studied. The FeNi layer allows the formation of the fcc lattice of FeMn, i.e. the antiferromagnetic γ-phase of FeMn. The Gd content was varied within 15-25 at. % in order to obtain different temperature dependences of the spontaneous magnetization M_s(T) of the Gd-Co layer. The magnetic properties of the films were determined from hysteresis loops measured in the temperature range 5-350 K. A correlation between M_s(T) and the temperature dependences of the exchange bias field H_(ebGdCo)(T) was established. In particular, it was shown that there is an inversion of the sign and sharp increase of the value of H_(ebGdco) near the magnetic compensation state. The first one is a consequence of the minimization of the spontaneous magnetization of Gd-Co layer at the compensation temperature. The second one shows the predominance of the exchange interaction of the antiferromagnetic layer with the cobalt magnetic sub-system of the ferrimagnetic layer as a contribution to the interlayer exchange coupling.