Thermal stability of sputtered GdDyFeCo films with trilayer structure

The thermal stability of GdDyFeCo films with trilayer structure has been studied by annealing in vacuum up to 300°C. In GdDyFeCo films sputtered on glass, the coercivity is reduced after annealing, which is thought to be due to a structural relegation caused by annealing. The saturation magnetization tends to increase upon annealing, in particular for rare-earth rich composition because of the increase of effective magnetic moment, making the compensation temperature (Tcomp) shift higher. The films with Tcomp between room temperature and 100°C show superior thermal stability, because their magnetic properties, especially Tcomp, change little after annealing. Overwrite repetition tests using magnetic field modulation recording also indicate that the disks with the Tcomp between room temperature and 100°C have superior overwrite durability. Small adjustments of the GdDy content seem to be effective in improving the thermal stability of GdDyFeCo films. The best Tcomp of the GdDyFeCo films is between room temperature and 100°C, and the optimum Dy:Gd ratio is between 45/55 and 70/30