Quantitative thermomagnetic analysis of CoCr films and experimental determination of the CoCr phase diagram

Publisher Website
Google Scholar
Abstract
We have experimentally determined the CoCr phase diagram in a region of great interest for magnetic recording media, by quantitative thermomagnetic analyses (TMA) of CoCr films. We used TMA results, together with CoCr bulk data, film‐average measurements of composition and room temperature Ms, and a novel curve‐fitting and analysis technique. Our TMA experiments suggested a model in which magnetic (exchange) energy causes the phase separation. There are four different phase diagrams for CoCr in the literature. Our experimentally determined phase diagram shows good qualitative agreement with the theoretical Hasebe phase diagram [J. Jpn. Inst. Met. 46, 577 (1982) (in Japanese)], the only one whose calculation included magnetic (exchange) energy terms. We have also estimated the relative amounts of the different phases present in the films, and found about 40 to 55 vol % to be nonmagnetic at room temperature. For such material, the magnetostatic contributions to magnetic anisotropy could be substantial.