Effect of Electron Concentration on Magnetic Properties of EuTe—GdTe

Abstract

The systems EuSe—GdSe and EuS—GdS show a strong increase in the positive value of the paramagnetic Curie temperature (θ) as a function of the Gd3+ concentration. The pure europium chalcogenides in both systems have positive θ values. This paper discusses the effect of the increase of electron concentration on magnetic interactions in EuTe, which is antiferromagnetic in its pure state. We find that θ increases from −10°K for EuTe to a maximum of +28°K for Eu0.8Gd0.2Te and then decreases monotonically with increasing Gd content to θ=−90°K for GdTe. The variation of θ is interpreted as a result of a Ruderman-Kittel-Yosida type interaction via the conduction electron donated by Gd3+. In contrast to the selenide and sulfide systems, no true ferromagnetic order occurs in EuTe-GdTe at 4.2°K for any composition. As an example, the magnetization of Eu0.8Gd0.2Te (θ=+28°K) saturates at 4.2°K for magnetic fields only above 45 000 Oe, which may be due to either spin canting or a more complex magnetic structure involving ferromagnetic clusters.