Structure Dependence of Magnetic Properties for Compositionally Modulated Films Including Rare Earth Metals as a Constituent

The dependence of magnetic properties on the layer structure of compositionally modulated Gd-Fe and Y-Fe films has been studied. It was found that by varying the periodicity of alternating layers, the structure of each layer can be controlled in a continuous way. In Gd-Fe films, samples with a period of less than 20 Ã… show a perpendicular anisotropy similar to that seen in amorphous film prepared by simultaneous evaporation, while films with each layer thickness 40 Ã… exhibit a "compensation temperature" due to a ferrimagnetic coupling between Gd and Fe layers. The magnetic behavior of Y-Fe films reflects changes in the structure more clearly than in the case of Gd-Fe system films. There exists a critical thickness for the Fe layer to complete a bcc structure. Below a critical thickness of 20 Ã…, the Fe layer is amorphous in nature; this, however, only occurs when the Fe layer is sandwiched between Y layers. Finally, recent studies on single crystal rare earth superlattices, including the Gd-Y and Dy-Y systems, are briefly reviewed.