The static and dynamic hyperfine interactions of radioactive ${}^{82}\mathrm{Br}$ in single-crystal hcp Co were measured with the techniques of nuclear magnetic resonance on oriented nuclei (NMR-ON), modulated adiabatic fast passage on oriented nuclei, and pulsed NMR-ON. The isotropic and anisotropic parts of the magnetic and electric hyperfine interaction with respect to the single-crystal c axis were determined. The principal component $V_{\mathrm{zz}}$ of the electric-field gradient tensor consists of an isotropic and an anisotropic part: $V_{\mathrm{zz}}^{\left(\mathrm{iso}\right)}$ is small but nonzero; $V_{\mathrm{zz}}^{\left(\mathrm{ani}\right)}$ has positive sign, in contrast to all other presently known impurity–hcp-Co systems for which $V_{\mathrm{zz}}^{\left(\mathrm{ani}\right)}$ is negative. The nuclear spin-lattice relaxation is considerably faster than expected from known data on Y, Nb, and Zr in hcp Co.

• Received 15 January 1999

DOI:https://doi.org/10.1103/PhysRevB.59.13948