Nuclear magnetic resonance study of Co‐CoO films for perpendicular magnetic recording (abstract)

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Abstract
Co‐CoO films, which are evaporated in the atmosphere of a small amount of O2, have large perpendicular magnetic anisotropy and show excellent read‐write (R‐W) characteristics. With heat treatment, the microstructure of a film changed and the R‐W characteristics were further improved.1,2 This result indicates that the microstructure of a film changed and the R‐W characteristics were further improved.1,2 This result indicates that the microstructure of a film closely relates with the R‐W characteristics as it does so for Co‐Cr films. We measured the spin‐echo spectra of a film having various magnetizations to investigate the relationships between R‐W characteristics and film microstructure, because NMR is very sensitive to the slight changes of film microstructure.1 A strong absorption was observed at 223 MHz which is for α‐Co. The intensity decreased drastically as the amount of oxygen in the films increased and very broad satellites appeared around 250 MHz, implying that Co atoms having a larger magnetic moment than that of α‐Co exist for the films containing oxygen atoms. Further, heat treatment increased the absorption intensity at 223 MHz, which means that the internal stress or the lattice defects were removed. The R‐W characteristics were found to relate with the absorption intensity. This result shows that the crystallinity of a film greatly influences the R‐W characteristics of Co‐CoO films.

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