A study of the magnetic phase diagram of the Cr-Si system near the tricritical point

In order to improve the understanding of the magnetic structures of alloys of the Cr-Si system in the vicinity of the tricritical point, the authors have performed neutron diffraction experiments on a crystal containing 0.85 at.% Si. They find that the temperature derivative of the wavevector Q of the incommensurate spin density wave state changes sign at approximately 230K: the Neel temperature of the alloy is 258K. They suggest that the Cr-Si phase diagram in the vicinity of the tricritical point has a re-entrant feature which has not been previously reported. This observation may lead to a better understanding of the mechanism of the first-order magnetic phase transition, from the paramagnetic state of the commensurate spin density wave state, which occurs in association with a large volume change in the Cr0Si and Cr-Fe alloy systems.