MAGNETIC-PROPERTIES OF EU SE SUPERLATTICES

The magnetization of rare-earth superlattices of Eu/Se grown on BaF2(1 1 1) by means of Molecular Beam Epitaxy (MBE) method has been measure d in order to clarify the mechanism for the anomalous magnetic propert ies. Selenium layers in the Eu/Se superlattice act as a separator betw een Eu layers and the thickness of Se layers was varied from 0.5 to 3 nm, while that of Eu layers was fixed at 1 nm. The crystal structure o f samples was characterized by X-ray diffraction and the in situ RHEED observations. A considerably good epitaxial structure was attained fo r [Eu 1 nm/Se 1 nm] sample, but [Eu 1 nm/Se 0.5 nm] and [Eu 1 nm/Se 3 nm] samples were only polycrystalline. The magnetization process measu red at 1.9 K shows that a magnetic phase transition takes place from a n antiferromagnetic to a spin-flop state. The critical magnetic field H-C is obtained at 3750, 2150 and 1000 G, respectively, for [Eu 1 nm/S e 0.5 nm], [Eu 1 nm/Se 1 nm] and [Eu 1 nm/Se 3 nm] samples. The exchan ge integral J is dependent on the distance between Eu-Eu layers, i.e., J proportional to d(-1.1). The magnetic phase diagram of Eu/Se superl attice has been obtained. (C) 1997 Elsevier Science Ltd.