| The effects of hydrogen absorption on the magnetic and structural properties of several rare earth - transition metal intermetallics were studied. The systems which were studied are: Th(,7)Co(,3), Th(,7)Ni(,3), CeNi(,4)Al, Th(,6-x)Y(,x)Mn(,23), R(,6)Mn(,23) (R = Gd, Tb, Dy, Ho and Er), Gd(,x)Y(,6-x)Fe(,23) and Er(,x)Y(,6-x)Fe(,23). The major findings obtained regarding each of these systems are as follows.; Neither Th(,7)Co(,3) nor Th(,7)Ni(,3) show any evidence of becoming magnetically ordered upon hydrogenation, contrary to the behavior observed previously for Th(,7)Fe(,3). The X-ray diffraction patterns of both hydrides are similar to that of Th(,7)Fe(,3).; CeNi(,4)Al acquires a large, temperature dependent susceptibility upon hydrogenation. This is in agreement with Takeshita's hypothesis of a partial conversion of Ce('4+) to Ce('3+).; Both the saturation magnetization and the ordering temperature of the Th(,6-x)Y(,x)Mn(,23) alloys decrease with decreasing x, long range order disappearing completely at x = 1.5. The hydride systems are all magnetically ordered: Th(,6)Mn(,23)H(,28) is ferrimagnetic, Y(,6)Mn(,23)H(,22) is antiferromagnetic, the hydrides of the Th-rich ternaries are ferrimagnetic and the hydrides of the Y-rich ternaries are mictomagnetic.; The R(,6)Mn(,23) (R = Gd, Tb, Dy, Ho and Er) hydrides appear to be either weakly ferrimagnetic or antiferromagnetic. Unlike the situation with the parent compounds, the detailed behavior of the hydridge systems is strongly dependent upon the nature of the rare earth.; The Gd(,x)Y(,6-x)Fe(,23) and Er(,x)Y(,6-x)Fe(,23) - hydrogen systems are magnetically very similar. In both cases the rare earth moment appears to be coupled antiparallel to that of Fe, in both the alloys and their hydrides. Although the magnetic coupling is unaffected, both the total magnetization (and hence the Fe moment) and the Curie temperature are significantly increased by hydrogenation. In some of the Er containing compounds absorption of hydrogen reduces the symmetry of the lattice (at room temperature) from cubic to tetragonal.; In addition to the magnetic studies a "counting" calculation showed that it is numerically possible to explain the observed reduction in hydrogen solubility when Al is substituted into LaNi(,5) in terms of near neighbor effects. |
