Direct observation of magnetically distinct regions in Co-Cr perpendicular recording media using ferromagnetic resonance

Abstract

We have used a 30-GHz resonant cavity spectrometer to record the ferromagnetic resonance (FMR) spectra characterizing several Co-Cr films. These films, 18–22 at. % Cr in composition, were characterized by net mean anisotropy K̄ extending from negative to positive in range. K̄ and M̄S are measured by a torque magnetometer (TM) and a vibrating sample magnetometer (VSM). FMR was used to measure the relative amounts and the corresponding 2K/MS and γ values of each of the magnetic constituents in a given specimen. Using integrated FMR intensities and corresponding 2K/MS, a reasonable correlation between the TM/VSM data and FMR was achieved. An initial study on four films indicates that poorly aligned specimens (Δθ50≂8°) are composed of several distinct magnetic constituents; well-aligned specimens (Δθ50≂2°) are characterized by a single constituent. Further, samples with larger Δθ50 all seem to be characterized by at least two constituents in common: one at 2K/MS≂0, the other at 2K/MS ≂−4πMS. This research, we believe, represents the first known confirmation by FMR of positive anisotropy in such Co-Cr films.