Abstract
The temperature dependence of lattice spacing of metastable C14-Laves phase RMn2 (R=Y, , Gd, , Dy and Yb) has been measured up to 300, K by X-ray diffraction. Large thermal expansion was observed especially for R=Y and Dy. GdMn2 shows a structural transition from hexagonal to orthorhombic below 80, K accompanied with a volume expansion. This indicates the appearance of a local magnetic moment of Mn 3d electrons with an antiferromagnetic order. The results are discussed together with the data on other stable C14-RMn2 and metastable C14-TbMn2. It is shown that the appearance of local magnetic moment of itinerant Mn 3d electrons of C14-RMn2 at low temperatures is mainly determined by the Mn-Mn distance. C14-YMn2, TbMn2 and DyMn2 are the critical substances for the onset of Mn moment.
