STRUCTURAL AND MAGNETIC STUDIES OF FE/NI MULTILAYERS

Compositionally modulated multilayer samples of Fe/Ni have been prepared in a dual-ion-beam sputtering system in which one beam is used to deposit the film and the other is directed at the substrate to increase the surface mobility of the arriving atoms. The multilayers had equal thicknesses of Fe and Ni, and wavelengths λ varying between 15 and 120 Å. The composition modulation was investigated by measuring the satellite intensities. The phases present have been studied by x-ray diffraction and extended x-ray-absorption fine-structure measurements. The x-ray investigations included Read photographs. The Ni layers have fcc structure. For λ=120 Å the Fe layers primarily have the usual structure of Fe, namely bcc. For λ<40 Å the Fe layers have fcc structure. For λ=50 Å the Fe layers are a mixture of fcc and bcc phases. The magnetic properties have been investigated by vibrating-sample-magnetometer measurements. For λ=35 Å, T=298 K, and the magnetic field parallel to the substrate, the coercive force is only a few gauss and, of more importance, the saturation magnetization is approximately the sum of the magnetization expected for bcc Fe and fcc Ni. For λ=35 Å, T=298 K, and the magnetic field perpendicular to the substrate, a field of 20 kOe is required to achieve saturation.