Thermal degradation behavior of amorphous GdFeCo alloy films with perpendicular anisotropy

Highlights: • A significant increase in magnetization is observed upon crystallization. • The crystallization temperature is determined to be around 450 °C. • Perpendicular anisotropy degrades rapidly with annealing and vanished before crystallization. • Significant change in magnetic properties is observed, in line with structural change. • The competition between oxidation and crystallization leads to pronounced change in sheet resistance. Amorphous perpendicularly magnetized GdFeCo films are fabricated by sputtering a composite target. Perpendicular magnetic anisotropy with a typical order of 10⁵ erg/cm³ in magnitude is achieved. The polarity of extraordinary Hall and magneto-optical Kerr loops indicates the films are Gd-dominant, confirmed by thermomagnetic measurement. A significant increase in magnetization is observed upon crystallization at ~450 °C. Perpendicular magnetic anisotropy is shown to degrade rapidly with annealing and vanishes before crystallization occurs, which can be ascribed to the structural relaxation in low temperature region. For the film annealed above crystallization temperature significantly reduced magnetization is observed, in line with the structural changes revealed by grazing incidence x-ray diffraction measurements. Pronounced change in sheet resistance of the films is observed in high temperature region, which can be attributed to the competition of two opposite contributions from the oxidation and crystallization. Our results provide some useful information for GdFeCo films used in device fabrication.