Magnetic properties of amorphous Gd-Fe films prepared by evaporation

Abstract

Amorphous GdxFe1-x films with 0.18<x<0.33 were prepared by electron-beam coevaporation of the elements. The composition dependence of anisotropy and the composition and temperature dependence of saturation magnetization of the films were studied. In contrast to evaporated Gd-Co films, where anisotropy is in-plane, the Gd-Fe films were found to have strong perpendicular anisotropy with the uniaxial anisotropy constant (K u) decreasing monotonically from 3.8×105 erg/cm 3 at x=0.18 to 2.0×105 erg/cm3 at x=0.33. The perpendicular anisotropy field (HK) reached a maximum at the compensation composition (x=0.26) and fell off rapidly on both sides. The findings suggest that anisotropy in evaporated films is due to a longer-range structural ordering than the pair ordering which is assumed to exist in sputtered films. Saturation magnetization measurements showed that magnetization of the amorphous alloys could be closely approximated from the moments of pure crystalline Gd and Fe. The 0 °K moment of Fe was found to be 2.20μB (0.23<x<0.31) suggesting less charge transfer than in crystalline GdFe3. Q values (HK/4πMs) of the alloys exceeded unity in the range 0.19<x<0.31.