Nuclear magnetic resonance in single crystals of dilute magnetic alloys

We have observed nuclear resonances from ⁶³Cu nuclei in the first few shells around Fe, Co, and Ni impurities present in low concentrations of single crystals of copper. The resonances appear as weak satellites displaced in field δH form the much stronger resonance from ⁶³Cu nuclei far from the impurities. Study of the dependence of the various δH's on the orientation of the static field →H₀, with respect to the crystal axes enables one to determine which satellites go with which shell of neighbors, and to deduce the quadrupolar, dipolar, and pseudodipolar coupling parameters for the observed shells. By these means we have been able to assign shells to satellites seen in powder samples. For CuFe we identify the second and third shells, for CuCo the first and second, and for CuNi the first. The observation that the pseudodipolar coupling of the first shell in CuCo is strongly nonaxial proves that there are strong crystal-field effects. For the first neighbor to the Co the pseudodipolar coupling is about twice the direct dipolar coupling. For CuFe the same is true for the third neighbor shell.