Influence of the magnetic state on the structure and thermal expansion in rare earth compounds

Using x-ray powder diffraction we investigated the thermal expansion of some selected nonmagnetic compounds (YAl₂, YNi₂ and YCo₂) and some isostructural magnetic Rare Earth-Cobalt compounds (RECo₂) in the temperature range from 4K up to 450 K. By comparing the nonmagnetic Y-based compounds we could show that there is a contribution of the spin fluctuations to the thermal expansion in YCo₂. In the magnetically ordering RECo₂ compounds the induced 3d-magnetism gives rise to large volume anomalies at the magnetic ordering temperature T_c. Below T_c there is also a distortion of the cubic unit cell because of the interaction of the magnetically ordered RE-ions with the anisotropic crystal field.