Noise characteristics in Co-Cr perpendicular recording media

Abstract

Noise characteristics in Co-Cr and Co-Cr/Ni-Fe perpendicular recording media were theoretically analyzed, based on an uncorrelated particle magnetization model. The analyzed results were compared with experimental results. Marked differences in noise spectra were found between single layer and double layer media, especially in the long wavelength region. The measured noise and signal spectra in a Co-Cr/Ni-Fe double layer medium were close to the numerically analyzed values for perpendicular magnetization, rather than for longitudinal magnetization. This indicates that the magnetization in the Co-Cr layer is directed almost perpendicularly. Furthermore, the measured noise power decreased with increasing the medium perpendicular anisotropy, which is closely related to the medium crystal orientation. As a conclusion, noise from Co-Cr perpendicular recording media is attributed to the medium grain magnetization direction dispersion, where the magnetizations are almost perpendicular to the medium surface.