Effect of High Pressure on the Order-Disorder Transition in CuPt

The order-disorder transition temperature T c of the alloy CuPt has been determined at pressures up to 80 kbar by the electrical resistance measurement technique. T c decreases almost linearly with increasing pressure at a rate of -0.9±0.1°C/kbar, making a striking contrast to the behaviors of the other ordering alloys hitherto studied. The observed pressure dependence of T c has suggested the existence of a high pressure modification, but an extended investigation including X-ray diffraction analysis on pressurized and quenched samples has shown that the L1 1 -type ordered structure remains stable at least up to 120 kbar.