Helical anisotropic magnetic film

Permalloy films have been evaporated onto glass substrates rotating with 0.05 to 450 r/m in a d.c. magnetic field. The magnetic uniaxial anisotropy was measured by using a torque magnetometer and the hysteresis loop was taken by using a 50 Hz hysteresis loop tracer. The magnetic anisotropy and the coercive forces,
H_{c\parallel}
and
H_{c\perp}
, which are measured along the easy and hard axes, respectively, were obtained as a functions of the angle of ratations during deposition. The uniaxial anisotropy is found to decrease with increases in the rotating angle. No anisotropy was observed with rotating faster than π/2 r/m. The ratio
H_{c\parallel}/H_{c\perp}
, however, increase gradually for rotations beyond π r/m and becomes unity after about 5 revolution. This final state corresponds to that for the film with isotropic magnetic properties. Its hysteresis loop is quite rectangle in all directions in the film plane. A similar trend was obtained even though the ratation speed, the substrate tempertature, and the film thickness have been widely changed. These characteristics could be explained phenomenologically in terms of the postulated assumpution with the helical alignment of uniaxial anisostropy oriented through the film thickness direction.