A MAGNETOELASTIC STUDY OF CR-FE ALLOYS

Measurements are reported of the temperature variation of the sound velocity and thermal expansion of 18 polycrystalline Cr-Fe alloys in the concentration range from 0.5 to 30 at.% Fe which covers the antiferromagnetic, spin-glass, re-entrant spin-glass, and ferromagnetic phases. In the antiferromagnetic phase, well defined anomalies in both the longitudinal velocity of sound and the thermal expansion coefficient were observed at the transition temperatures. The magnetic contributions to the volume strain (DELTA-omega) and bulk modulus (DELTA-B) have been found to fit the equations DELTA-omega = SIGMA(n = 0)2 A(n)T2n and DELTA-B = SIGMA(n = 0)2 B(n)T2n rather well up to temperatures close to the Neel temperature. In the spin-glass phase, anomalies in the velocity of sound were observed between 4 and 150 K. These anomalies could not be attributed solely to spin-glass transitions as antiferromagnetism may still exist in these Cr-Fe alloys. In the ferromagnetic region no anomalies in either the velocity of sound or thermal expansion were observed at the Curie temperatures.