Annealing Behavior and Temperature Dependence of the Magnetic Properties of Thin Permalloy Films

Permalloy films are evaporated in a vacuum of 10−5 mm Hg in the presence of a magnetic field to achieve a uniaxial anisotropy. All annealing treatments and magnetic measurements are performed simultaneously in a vacuum of 10−8 to 10−7 mm Hg. In a film never heated above the deposition temperature, the temperature dependence of the uniaxial anisotropy is stronger than in bulk Permalloy, and magnetic annealing changes the anisotropy even at temperatures below 350°C. These changes are strongly dependent on whether or not the magnetization is aligned in the hard direction during cooling. During annealing above 400°C the coercive force is increased, and subsequent magnetic annealing treatments exhibit kinetics similar to those of bulk material.