Magnetoelastic behaviour in dilute Cr-Co alloys

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Abstract
Measurements of the temperature dependence of the thermal expansion and elastic constants of polycrystalline Cr and Cr-Co alloys having compositions 02 up to about 0.6 TN in good agreement with the theory of magnetoelastic behaviour of itinerant electron magnetic systems. Rather large anomalies in the bulk moduli around TN have been observed but none in the shear moduli. The calculated values of the anomalies in the bulk moduli are about two times larger than those observed at zero temperature. Furthermore, these anomalies are observed to increase with increasing temperature, reaching their highest values near TN, in contrast to the theoretical prediction that the anomalies should decrease with increasing temperature. In the case of the 6.09 at.% Co sample, which displays a jump-like behaviour in both the bulk modulus and the thermal expansion coefficient, the results are in agreement with a thermodynamic relation based on Walker's theory (1980) for second-order transitions, i.e. Delta beta dTN/dp= Delta kappa where Delta beta and Delta kappa are the anomalies in the volume thermal expansion coefficient and the compressibility, respectively.