Thickness dependent crystallographic transition in Fe/Ni multilayers

Abstract

The crystallographic transition between bcc- and fcc-structures has been studied in Fe/Ni multilayers with Mössbauer spectroscopy and X-ray diffraction. Layered structures have been confirmed and the structures depends both on individual layer thickness and the ratio of the constituents. Two sets of samples are made: the Fe layer thickness kept constant to 12 monolayer (ML) and 24ML, while the Ni layer thicknesses varied from 3 to 12ML. When the Ni layer is thin, the Fe/Ni multilayers have the bcc phase. When the thickness of Ni layer reaches 6ML and larger, a gradual transition to the fcc phase occurs. Mössbauer spectroscopy studies confirm the existence of a magnetic Fe bcc phase with in-plane magnetization in all samples, two magnetic fcc phases with fields of 28 T and 10 T and small amounts of nonmagnetic fcc phases in the thicker films. The observed behaviour can be attributed to the existence of two types of interfaces which are not necessary overlapping each other: An elemental interface between Fe and Ni and a structural interface between fcc and bcc phases. © 2010 IOP Publishing Ltd.