On magnetic first-order transitions in Cr-rich Cr-Fe and Cr-Si alloys: latent heat and susceptibility studies

There are only two binary chromium alloy systems, CRFe and CrSi, which exhibit an abrupt change in their physical properties due to a paramagnetic-commensurate spin density wave type of antiferromagnetic ordering. This property of an impurity broadening the initial weak first-order transition of the matrix and then bringing about a large first-order transition without any accompanying significant change in its crystal structure is unusual. The authors present precision calorimetric and magnetic susceptibility studies on alloys with concentrations especially close to the tricritical point in a temperature versus concentration plane of the magnetic phase diagram for these systems. The latent heat studies correlate well with the pressure dependence of TN, satisfying the Clausius-Clapeyron relationship. While the nature of the physical mechanism responsible for these transitions remains largely unexplained, the results suggest a possible common origin for the first-order transitions in these systems.