Correlations of modulation noise with magnetic microstructure and intergranular interactions for CoCrTa and CoNi thin-film media

This paper reports on two thin-film media alloys Co86Cr12Ta2 and Co75Ni25 which have very different noise characteristics. The magnetic microstructure of these films was observed with scanning electron microscopy with polarization analysis (SEMPA). The variance (σ 2t) of the magnetization across the transition region was calculated. The origin of anisotropy was determined by measuring the temperature coefficients of Hc and Ms. The interaction strengths between grains, δM(H), were obtained from the measurements of the reverse demagnetization remanence Md(H) and the forward magnetization remanence Mr(H). We found that the CoNi film showed a greater degree of interparticle interaction, which may explain the observed cross-bit linkages in SEMPA image, larger rms transition variation (σt), and higher modulation noise.