MAGNETIC AND STRUCTURAL-PROPERTIES OF CERIUM IRON MULTILAYERS

Ce/Fe multilayers with modulation lengths between 18 and 200 angstrom were prepared by ion-beam sputtering in an UHV system and structurally characterized by X-ray diffraction at small angles and Fe-57 conversion-electron Mossbauer spectroscopy. Good periodicity and sharp concentration profiles at the interfaces are found. The magnetic properties are unusual. For Fe-layer thicknesses below 25 angstrom, relatively independent of the Ce-layer thickness, the Curie temperature is reduced to values below 180 K. This is accompanied by a distinct decrease of the spontaneous magnetization and the appearence of hysteresis in the low-field susceptibility at low temperatures. Isothermal magnetization curves point to noncollinear magnetic order. Evidently, these phenomena are closely related to the transition in the Fe layers from the bcc cystalline to an amorphous structure occurring near 25 angstrom according to X-ray diffraction at large angles and RHEED diagrams.