Thermal-expansion anomalies and spontaneous magnetostriction of Lu2Fe17−xSix intermetallic compounds

Abstract The thermal expansion of Lu 2 Fe 17− x Si x solid solutions has been measured by X-ray powder diffraction. The magnetic ordering in all compounds within the homogeneity range ( x ⩽3.4) is accompanied by a large spontaneous volume magnetostriction, distributed anisotropically over the principal axes of the hexagonal crystal structure. The volume effect ω s in the ground state reaches 14.7×10 −3 in Lu 2 Fe 17 and decreases monotonously to 8.9×10 −3 for x =3.4, following the reduction of magnetic moment. Despite a still large ω s , the Invar behavior observed in Lu 2 Fe 17 changes to a positive thermal expansion for x >1 due to an increasing Curie temperature.