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

Abstract

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 ${10}^{\text{−8}}\hspace{0.17em}\mathrm{mm}$ Hg, and the measurements are carried out in the vacuum system at pressures below ${10}^{\text{−9}}\hspace{0.17em}\mathrm{mm}$ . 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 $K_u$ 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 $\text{1−f\hspace{0.17em}=\hspace{0.17em}}\exp {\mathrm{(-t/\tau )}}^{\frac{1}{3}}$ , and ${\text{1/τ\hspace{0.17em}=\hspace{0.17em}1/τ}}_0\hspace{0.17em}\exp \text{(−9000/RT)}$ .