Mechanism for the Direct Exchange Interaction of Europium in Compounds with Rocksalt Structure

Abstract

From the strong decrease in the nearest‐neighbor exchange interaction going from EuO to EuS, EuSe, EuTe, it has been concluded that this positive interaction must be caused by direct orbital overlap. Since the 4f cores are very small, this has to occur via partial occupation of outer orbits. The excitation to the 5dwave function by zero point lattice vibrations has been considered and is thought to be responsible for the ferromagnetism of these compounds. The order of magnitude has been estimated and agrees with experiment.