Magnetic Behavior of R2Fe14B Hydrides (R = Gd, Tb, Dy, Ho and Er).

摘要

R2Fe14B systems, with R = Gd, Tb, By, Ho and Er were hydrogenated to the composition R2Fe14BH x where x ranges from 3.7 to 5.4. The pressure-composition isotherms (PCIs) of the hydrides showed only a solid solution behavior. No plateau pressure region was observed between room temperature and 300 C and at pressures down to 10-2 atm. The absorbed hydrogen leads to an increase of 2.6 to 3.4% in unit cell volume, without a change in crystal structure. Magnetic characteristics of the present compounds were investigated over the temperature range 4.2 to 1100 K and at applied field up to 20 kOe. Saturation magnetization, Ms, and magnetic ordering temperature, Tc, were enhanced upon hydrogenation Tc is found to be dependent on the hydriding composition. Hydrogen induces a spin-reorientation effect (SR) in Gd- and Dy-containing compounds, while it has a marked influence in raising the spin-reorientation temperature, TSR, in the Er2Fe14B compound. The hydride involving Tb appears to remain uniaxial to the lowest temperature studied. In all cases the anisotropy fields, HA, were significantly reduced by hydrogen absorption. Reprints. (js)