NMR Studies of Pd–Rh and Ni–Rh Alloys

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Abstract
Low‐temperature (T ≈1°–4°K) measurements of the Knight shift (K), spin‐lattice relaxation time (T1), and inhomogeneous linewidth (Δ) of 103Rh in the two alloy systems Pd1−x–Rhx (0.03 ≤ x ≤ 1.00) and Ni1−x–Rhx (0.38 ≤x ≤1.00) have been carried out using transient NMR techniques. In Pd1−x–Rhx both T1T and K vary monotonically with decreasing x, K decreasing from +0.43% to −14.4% and T1T from 9.2 to 0.8 sec°K. The minimum K value agrees with the infinite dilution value K = −14.7% obtained by Rao, Matthias, and Shirley using PAC techniques, and indicates that K is essentially independent of x for Rh concentrations up to ∼5 at.%. The threefold increase in K for 103Rh as a dilute impurity in Pd over that of 105Pd in the elemental metal indicates that the local susceptibility at the Rh sites exceeds that of the Pd sites. Similar results are found in Ni1−x–Rhx with K decreasing from +0.43% to −8.1% and T1T from 9.2 to 1.2 sec°K. However, the susceptibility at the Rh sites appears to be smaller than at the Ni sites in this case. Both alloy systems display severe inhomogeneous broadening of the NMR with Δ ≈ K in some cases. This result demonstrates an extreme sensitivity of the local susceptibility to the near‐neighbor environment.

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