STRUCTURE AND ENHANCED MAGNETIZATION IN FE PT MULTILAYERS/

A series of Fe/Pt multilayers, prepared by magnetron sputtering, were characterized by structural [x-ray diffraction (XRD), x-ray-absorption spectroscopy, extended x-ray-absorption fine structure, TEM] and magn etization techniques and extensively investigated by Mossbauer spectro scopy. The Fe layer thickness varied from 3 to 60 Angstrom and that of Pt from 5 to 39 Angstrom. The 3 Angstrom Fe/9 Angstrom Pt sample disp lays magnetic hyperfine structure at room temperature (RT) while the 3 Fe/19 Pt sample is paramagnetic at RT, demonstrating the effect of th e interlayer interaction. Both samples display out of plane magnetic a nisotropy with a 39 degrees angle with respect to the normal for the f ormer and 20 degrees for the latter. As the Fe layer thickness increas es the magnetic vector turns to the plane. Systematic analysis of the Mossbauer spectra of samples with increasing Fe layer thickness allowe d the determination of the magnetic hyperfine field for each Fe monola yer within the Fe layer slab. Hyperfine fields larger than the bulk Fe value appear in all samples with Fe layer thickness larger than 3 A, and display an oscillatory dependence on the distance of the correspon ding Fe monolayer from the interface. These hyperfine field values sca le linearly with the average interplanar distance of the Fe layer deri ved from the refinement of the XRD data for each sample. Fe atomic mag netic moments determined from superconducting quantum interference dev ice magnetometry and Rutherford backscattering spectroscopy measuremen ts are also larger than the bulk Fe value, approaching it for large Fe layer thickness. The parameters determining the. enhancement of magne tization in the Fe/Pt system are discussed.