Non-uniform Gd distribution and magnetization profiles within GdCoFe alloy thin films

Abstract

Rare earth (RE):transition metal (TM) ferrimagnetic alloys continue to attract significant attention for spintronics. This work focuses on the elemental distribution of RE and TM elements throughout the thickness of nominally uniform films and the resulting spatial variations of the magnetization within these layers. Samples of CoFe alloyed with Gd were studied using secondary ion mass spectroscopy, polarized neutron reflectometry, and x-ray resonant magnetic reflectivity. The samples were grown by magnetron co-sputtering to control the RE:TM alloy ratio of the ferrimagnetic layer, which was combined with W and Pt layers as either under or over-layers to create sample structures such as W / Gd- x ( Co (70) Fe- 30 ) (100 - x) / Pt, where x = 0, 8, and 23 at. %. Results show that uniformly deposited thin-films have a significant variation in the distribution of the TM and RE through the film thickness, and this leads to a spatial distribution in the net magnetization profile and a non-uniform Gd magnetization profile within the layer. These findings have implications for the application RE:TM alloys in spintronics as they may impact the perpendicular magnetic anisotropy, the ferrimagnetic compensation temperature, and interfacial spin transport.