The Magnetic Anisotropy of Iron-Nickel (50–50) Thin Film Induced by Neutron and α-Particle Irradiation

Abstract

Measurements of the magnetic anisotropy induced by irradiation of reactor neutrons or 1.47 MeV α-particles at 563°K in a magnetic field of about 2000 Oe were made on the evaporated Fe–Ni (50%–50%) thin films of single and polycrystalline structures. The observed induced uniaxial anisotropy was a few times larger than that of the bulk alloys. The temperature dependence of this anisotropy was measured at temperatures from 77°K to 663°K and fits quite well with the third power of the magnetization. Above 573°K, the magnetic anisotropy decreases with increasing temperature and time of heat treatment. The temperature dependence is well described by assuming the activation energies of 0.55 eV between 573°K and 773°K and 2 eV about 773°K.