Magnetically induced phase separation in the Co-Cr binary system

Direct evidence of phase separation in the Co-rich corner of the Co-Cr bina ry system, the transformation of high-temperature FCC alpha -Co into a ferr omagnetic alpha (f) phase and a paramagnetic up phase, has been experimenta lly obtained by using diffusion couple technique, scanning electron microsc opy with energy dispersion analysis of X-ray (SEM-EDX), analytical transmis sion electron microscopy, optical microscopy and X-ray diffraction. Thermod ynamic calculation, on the basis of the presently obtained phase equilibriu m data, has verified that this phase separation arises from magnetic orderi ng, and that a similar phase separation appears in the HCP phase below 469 degreesC which is transformed into a ferromagnetic epsilon (f) phase and a paramagnetic epsilon (p) phase. It is therefore concluded that magnetically induced phase separation must be responsible for the microscopic compositi on modulation of Cr in the CoCr thin film magnetic recording media. (C) 200 1 Elsevier Science B.V. All rights reserved.