Magnetic Anisotropy of Metal-Evaporated Tapes

The oblique magnetic anisotropy of metal-evaporated tapes for audio recording has been studied, using ferromagnetic resonance techniques at 34 GHz. The static field was rotated in the tape plane and the vertical plane. The resonance equation in the tape plane was derived without approximation. By fitting the data for the resonance field (Hr) to the equation for the tape plane, the following values of the saturation magnetization (4¿M), the intrinsic anisotropy field (Hk), and the angle of inclination of the anisotropy axis from the film normal (¿) were determined: 4¿M=9.63 kG, Hk=1.06 kOe, ¿=60.0°. The resonance fields in the vertical plane also closely fit the theoretical curve, except for a few data points in high-field regions. The effect of surface roughness on Hr is discussed.