Magnetically induced phase separation in the Co-Cr binary system

Direct evidence of phase separation in the Co-rich corner of the Co-Cr binary system, the transformation of high-temperature FCC alpha -Co into a ferromagnetic alpha (f) phase and a paramagnetic up phase, has been experimentally obtained by using diffusion couple technique, scanning electron microscopy with energy dispersion analysis of X-ray (SEM-EDX), analytical transmission electron microscopy, optical microscopy and X-ray diffraction. Thermodynamic calculation, on the basis of the presently obtained phase equilibrium data, has verified that this phase separation arises from magnetic ordering, 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 composition modulation of Cr in the CoCr thin film magnetic recording media. (C) 2001 Elsevier Science B.V. All rights reserved.