The frequency dependence in the equivalent circuit of an electrical steel sheet core was improved by the use of a new equivalent circuit, in which each parallel circuit consists of a real inductance, an imaginary inductance, and a resist- ance, which are related to a permeability, a hysteresis loss, and an eddy current loss, respectively. The parallel circuits are connected in series in order to represent the distribu- tion of magnetic properties in an electrical steel sheet as regards their polycrystal and texture. The distribution coefficients of both hysteresis loss and eddy current loss are 0.6-1 for non-oriented electrical steel sheets, and 0.1-0.6 for grain-oriented electrical steel sheets. The frequency dependence of the impedance of a new equivalent circuit is consistent with those of the permeability and iron loss of an electrical steel sheet, measured with a modified Hay bridge.
This paper discusses the relationship between the effective write track widths of thin-film heads and the coercivities of thin-film disks. The off-track performances of the output amplitudes and media-noises were investigated by using Co-Cr-Ta sputtered thin-film disks with different coercivities. The effective write track width becomes larger with an increase in the disk coercivity if the gradient of the head write field is large. If the gradient of the head write field is small, the wavelength of the zigzag wall becomes short and its amplitude becomes large in the track width direction of the transition regions. At the track edges of the transition regions, the track width direction component of magnetization increases because of the bitpattern bridging between the neighbor transitions.
Overwrite characteristics are calculated by using a model in which erasure is incomplete because of the small head field, and in which phase modulation occurs as a result of the shifts in the locations of the transitions as causes of overwrite noise. If account is taken of the demagnetizing field from the leading-edge transition, which is found to be significantly affected by head-gap length and write core saturation, the calculated results show good agreement with experimental results for various values of the magnetomotive force, head-medium spacing, and recording density. It is found that a high head-field gradient as well as a large field is required to achieve good overwrite for high recording density; overwrite characteristics are therefore adversely affected by head pole saturation. NiFe/ CoNiFe (high Bs} laminated heads, which are able to keep the field gradient high, have better overwrite characteristics than NiFe heads.
Lubricants on a thin-film magnetic recording disk were analyzed by using TOF-SIMS. The lubricants used were Fomblin-AM2001, Fomblin-Z. DOL, Fomblin-Z, DEAL, Fomblin-Z. DIAC, Krytox-143AD, and Krytox-157FSH of perfluoropolyether.The main structures of Fomblin and Krytox were distinguished by a negative mass fragment pattern and a peak height ratio of m/z = 69 (CF3+) : m/z =119 (C2F5+). The end groups of Fomblin-AM2001, Fomblin-Z. DOL and Fornblin-Z. DIAC were detected by means of the fragment ions of the end groups. Damage to the lubricant film in the wearing region on the disk was then investigated by using TOF-SIMS. As a result, it was considered that the main structures were decomposed more than the end groups, when the head contacted the lubricant film.These results showed that the sensitivity and resolution of TOF-SIMS was higher than that of quadruple static SIMS. It was found that the TOF-SIMS measurement provides useful information on the durability of a thin-film magnetic recording disk.
The effect of an alternating field on an M-H loop shape was investigated by using an alternatinggradient-force magnetometer on several film samples with different coercivities. It was found that the coercivity became larger with a decrease in the alternating field at the sample edge and reached a constant value at the lower alternating field. The magnitude of the alternating field at the sample edge for obtaining precise M-H loops was discussed quantitatively.