Influence of the Fe content on the Gd magnetic ordering temperature in Ni1-xFex/Gd multilayers

Abstract

We explore the influence of Fe content on the interfacial magnetic properties of Ni1-xFex(50 angstrom)/Fe (t angstrom)/Gd(50 angstrom)/Fe (t angstrom)/Ni1-x Fe-x(50 degrees) (x = 0.2 and 0.6, and t = 0 and 10 angstrom) multilayers by means of element-specific x-ray magnetic circular dichroism measurements at Gd M-5 and (Ni, Fe) L-2,L-3 absorption edges, superconducting quantum interference device magnetometry, and specular reflectivity measurements. Increasing Fe content in the Ni-Fe layer enhances the Gd ordering temperature in the interfacial regions. Addition of a 1-nm Fe spacer results in the largest enhancement in Gd ordering temperature in both interior and interfacial Gd regions, even for high Ni content in the Ni-Fe layer. This indicates that the Fe spacers act as effective barriers (albeit imperfect) in reducing Gd-Ni contact interactions responsible for limiting the interfacial Gd magnetic ordering temperature to values larger than bulk Gd, but significantly lower than observed at Fe/Gd interfaces.