Heat-Induced Effective Exchange: A New Coupling Mechanism in Magnetic Multilayers

Abstract

The effective exchange interaction between two ferromagnetic layers separated by a semiconductor spacer layer is found to be reversibly heat induced. First we present experimental data on Fe/a-ZnSe/Fe trilayers. We report the thickness and temperature dependences of the exchange energy. In order to model the observations we then study a coupling which is mediated via impurity states situated at the interfaces of the layers. Weakly bound impurity states may interfere across the spacer layer. The interaction of these “molecular orbitals” depends on the spin configuration of the electrons. Thermal repopulation of the impurity levels yields a positive temperature coefficient of the coupling. The results of the calculations are found to reproduce well the experimental observations.