EFFECT OF MAGNETIC-ANISOTROPY ON MAGNETIC RECORDING HEAD CHARACTERISTICS

Anisotropy of permeability for single-crystalline Mn-Zn ferrite and its influence on head characteristics are investigated. The angular dependence of permeability is measured using disc-shaped ferrite samples, whose surfaces are the (110) plane. The easy axis of magnetization in the (110) plane is observed to change from the [001] to the [1̄10] direction with increasing residual surface tention resulted from machining. At low frequencies, maximum permeability is observed when measured along the easy direction, while it is observed in the hard direction at high frequencies. This indicates a change in the dominant magnetization process from “domain wall motion” to “spin rotation” with changes in measuring direction and frequency. The transition frequency, obtained from the angular dependence of permeability, depends upon this residual stress and ranges between 0.5 and 2 Mz. Two types (A and B) of heads with the same geometry but different crystalline orientations, as shown in Fig.1 are prepared using the Mn-Zn ferrite described above. For simplicity of the analysis, the protection glass is etched off. It's observed that at the frequencies lower than 6 Mz, the read-back signals obtained with the A-type heads are higher than those obtained with the B-type heads and v.v. at higher frequencies. In contradiction to the expectation from the results on the disc-shaped samples, it is confirmed from the behavior of the Q-factor, that the easy axes lie in the [001] direction even in the neighborhood of head gap portion, indicating the existence of axial stresses perpendicular to the head gap plane. This explains the frequency dependence of the head characteristics described above. © 1979 IEEE