O2 contaminated amorphous FeGd films

Abstract

Amorphous FeGd films were made by thermal evaporation in an ultra high vacuum system under controlled O₂ pressures. The Gd necessary for magnetic compensation at room temperature increases from 20.2 to 23.8 at.% with increasing O₂ pressure from 5×10⁻⁸ to 3×10⁻⁷ Torr. The perpendicular magnetic anisotropy K_u of films whose composition is about 1.5 at.% Gd deficient compared to the room temperature compensation composition decreases from 2.4×10⁵ erg/cm³ at 8×10⁻⁸ Torr O₂ to 1.2×10⁵ erg/cm³ at 3×10⁻⁷ Torr where part of the magnetic material starts to develop in‐plane anisotropy which increases with increasing O₂ pressure to 100% at 5×10⁻⁷ Torr O₂. Further O₂ increase yields superparamagnetic films. Between 5×10⁻⁸ and 3×10⁻⁷ Torr O₂ pressure H_c drops from ≳50 Oe to 2 Oe. The electrical resistivity exhibits an exponential increase above 2×10⁻⁷ Torr O₂. A model to explain these findings will be proposed.