Powder X-ray diffraction measurements on intermetallic compounds RMna (R: Y, Pr, Nd, Sm and Gd) have been made in a temperature range from 69 to 300 K. Below Tn, every sample shows a large volume expansion, being as large as 4.6% for YMn2. In addition, PrMna and NdMn2 having the hexagonal C14 type of crystal structure are distorted into monoclinic below Tn- On the other hand, SmMn2 having the same C14 type structure is distorted into orthorhombic. On the basis of a theory of magnetoelastic coupling the directions of magnetization of these compounds below were determined. The cubic Cl5 type YMna shows a very small and probably rhombohedral distortion below Tn, whereas the same Cl 5 type GdMni shows no symmetry change.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)