Magnetic Anisotropies of Nickel Films Evaporated and Measured at 10−8 mm Hg and Below

The magnetic anisotropies in evaporated polycrystalline nickel films have been measured with a torque magnetometer over a range of fields from 10 to 2000 oe. The films are deposited in a vacuum better than 10−8 mm Hg, and the measurements are carried out in the vacuum system at pressures below 10−9 mm. The magnitude of the induced uniaxial anisotropy has been measured as a function of temperature up to the Curie point of nickel (360°C), and the kinetics of the magnetic annealing process have been measured from room temperature to 200°C. The anisotropy Ku decreases roughly linearly with temperature above room temperature, reaching zero near the Curie temperature. If f is the fraction of the annealing process completed at a given temperature, we find that 1−f = exp(−t/τ)13, and 1/τ = 1/τ0 exp(−9000/RT).