Hydrogenation and Anisotropic Expansions in R_3Fe_(29-x)T_x (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

摘要

A systematic study of the phase formation, structure and magnetic properties of the R3Fe29-xTxcompounds (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr) has been performed uponhydrogenation. The lattice constants and the unit cell volume of R3Fe29-xTxHy decrease withincreasing R atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction.Regular anisotropic expansions mainly along the a- and b-axis rather than along the c-axis areobserved for all of the compounds upon hydrogenation. Hydrogenation leads to an increase inthe Curie temperature and a corresponding increase in the saturation magnetization at roomtemperature for each compound. First order magnetization processes (FOMP) occur in theexternal magnetic fields for Nd3Fe24.5Cr4.5H5.0, Tb3Fe27.0Cr2.0H2.8, and Gd3Fe28.0Cr1.0H4.