Magnetization Fluctuations and Characteristic Lengths for Sputtered CoPICr Thin Film Media

intergranular exchange; correlation length; media noise Magnetization fluctuations of uniformly magnetized media have been measured in sputtered CoP thin films as a function of Cr underlayer thickness. Increasing underlayer thickness from 20 om to 400 om yields decreasing magnetization fluctuation noise from 210 om to about 25 om, similar to the known decrease of transition noise. For every disk but one, the noise power dependance on magnetization is well fit by the square of thewagnetization vs. current loop derivative, (dM/dl,Y'. Thus, the noise mechanism appears to follow a modulation process independent of noise level. Analysis of measured magnetization noise spectra yields approximate correlation lengths which decrease with increasing Cr underlayer thickness