In order to examine possible sources of the discrepancies between the proton NMR parameters for ${\mathrm{ZrH}}_{\mathrm{x}}$ as reported by R. C. Bowman, Jr., et al. [Phys. Rev. B 27, 1474 (1983)] and C. Korn [Phys. Rev. B 28, 95 (1983)], proton spin-lattice relaxation times ($T_1$), lattice parameters, and magnetic susceptibilities (χ) have been measured for high-purity ${\mathrm{ZrH}}_{\mathrm{x}}$ samples in the composition range 1.5≤x≤1.9 that had been typically annealed at 525 °C for 21 d. When these results are compared with the corresponding parameters obtained on the as-prepared ${\mathrm{ZrH}}_{\mathrm{x}}$ samples of Bowman et al. it was found that the anneals generally had only minor effects on the proton $T_1$ values, lattice parameters, or χ(T) behavior. The most notable exception is a ${\mathrm{ZrH}}_{1.70}$ sample that was initially composed of a mixture of δ(fcc) and ε(fct) phases and converted to just the ε phase upon annealing. Although the anneals gave small systematic decreases in the unit-cell volumes, the tetragonal distortions (i.e., c/a ratios) were not affected within experimental accuracy. Furthermore, both the proton ($T_1$T${)}^{\mathrm{-}1/2}$ peak and $T_1$T temperature dependences were also not significantly changed by these anneals. Although the χ(T) values in the ε phase decrease rapidly with increasing hydrogen content, a local χ(T) maximum that reflects the Pauli component from a peak in the Fermi-level density of states is observed near x=1.80. The dominant χ(T) decrease is primarily attributed to reductions in the orbital contribution with the increasing tetragonal distortion. Variations in the concentrations and distributions of oxygen and paramagnetic impurities are believed to be responsible for most of the differences found in the previous studies.

• Received 14 December 1984

DOI:https://doi.org/10.1103/PhysRevB.31.5604