SILICON GRADIENT RELATED PHASE COEXISTENCE IN Cr-Si?

Previous work on a single crystal of Cr-0·6%Si observed that the transition from the paramagnetic (P) to the incommensurate (I) antiferromagnetic phase was spread over a range of temperature from 272K to 282K. This could imply the presence of a new magnetic phase within this temperature range, or the inhomogeneous distribution of silicon throughout the crystal. Measurement of the C44 elastic constant was undertaken at the P-I transition (T < t> 272K) as well as at the spin flip transition (T <1 > 101K), and were complemented by a neutron diffraction topography study undertaken across the spin flip transition. The investigation was carried out in two stages, prior to annealing with the as prepared crystal, and also after annealing in an inert argon atmosphere. These data can be explained through the presence of an uneven silicon gradient throughout the sample, which also accounts for the extended width of the transition as previously observed. From the width of the spin flip transition it is possible to infer a compositional variation of 0·6 + 0·05% silicon content across the samples. An approximate 20 percent reduction in the inhomogeneity was observed after annealing.