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The hyperfine interaction of 192Ir nuclei as dilute impurities in Fe and Ni has been investigated with NMR on oriented nuclei. With the use of highly dilute and pure alloys the line widths could be reduced so far that the quadrupole splitting of 192IrF__ee and 192IrNi could be resolved. Taking hyperfine anomalies into account the ground state nuclear moments of 192Ir are deduced as 1#1=1.924(10) /~N and Q=2.36(11) b. The hyperfine field of IrNi was investigated as a function of the Ir concentration c between 0.01 at ~o and 5 at ~. The dependence of HHF on C was found to be significantly smaller than that reported from MiSssbauer effect measurements. For c=0.01at~ HHF= --454.7 (2.3)kG is deduced. The resonance shift with an external magnetic field has been studied precisely, yielding K = 0.012 (23) and K = 0.026 (12) for the Knight-shift of 192Ir in Fe and Ni, respectively. m -' 7-", Bolt zmGnn slow-r el0.xat ion f0.st -relaxation distribution limit limit t << T 1 t >>T 1 \ \ \., "d 2 \\

The electric quadrupole interaction of 188 Ir ͑I p 1 2 ; T 1͞2 41.5 h͒ in a Fe single crystal was measured for magnetization parallel to the crystallographic [100], [110], and [111] axes. Contrary to all previous experiments, a strong dependence of the electric field gradient on the direction of the magnetization with respect to the crystallographic axes was observed for the first time.[ S0031-9007(97) PACS numbers: 76.60. Jx, 75.50.Bb, 76.60.Gv, 76.80.+ y The electric field gradient (EFG) at the site of impurity nuclei in cubic ferromagnetic hosts such as Fe, Ni, and fcc-Co has been the subject of many investigations, both experimental [1-9] and theoretical [5,10,11]. It was first observed by nuclear magnetic resonance (NMR) of where eq V zz (henceforth denoted as EFG) is the principal component of the traceless EFG tensor and eQ is the nuclear spectroscopic quadrupole moment. If the EQI is collinear with the magnetic hyperfine interaction, the magnetic resonance frequency is split into a set of 2I equidistant subresonances, where I is the nuclear spin. The subresonance separation is given byThe satellite resonances were considerably broader than the central line. Mainly, the following two explanations were discussed: (i) The additional broadening is due to lattice inhomogeneities. (ii) The EFG depends on the direction of the magnetization with respect to the crystal axes. To explore whether the second possibility was the origin for this broadening, Aiga and Itoh prepared single crystal alloys of Fe-0.3% Ir by the stress annealing method. The NMR measurements yielded exactly the same spectra as observed for the polycrystal samples [5]. Thus Aiga and Itoh concluded that the quadrupole interaction is almost independent of the direction of the magnetization, and even if there is some anisotropy, it is of the order of, or less than, a few hundred kHz. Johnston and Stone performed NMR on oriented nuclei (NMR-ON) measurements on 192

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