Quantitative evaluation of magnetocrystalline anisotropy of columnar grains and thickness of initial layer in CoCr-based perpendicular media

We propose a quantitative analysis using perpendicular torquemetry to evaluate the thickness of the initial layer which consists of nanocrystalline grains, whose c axes are three-dimensionally randomly oriented, and the intrinsic magnetocrystalline anisotropy of the columnar grains with its c plane parallel to the film plane for CoCr-based perpendicular thin-film media. By applying this analysis to CoNiCrTa, CoCrPtTa, and CoCrPtB media, we found that the initial layer can be completely removed in the CoCrPtB medium epitaxially grown on an hcp-structured Co60Cr40 intermediate layer.