Anomalous temperature dependence of the hyperfine field on osmium in nickel

Using the ion-implantation perturbed-angular-correlation technique, the temperature dependence of the hyperfine field effective on osmium in nickel has been studied. First-excited states of ${}_{}{}^{188}{}_{}{}^{}\mathrm{Os}$ and ${}_{}{}^{192}{}_{}{}^{}\mathrm{Os}$ with known lifetimes and magnetic moments were used as probes of the magnetic interaction. The reduced hyperfine field $\frac{H\left(T\right)\mathrm{}}{H\left(0\right)\mathrm{}}$ differs markedly from the nickel reduced bulk magnetization $\frac{M\left(T\right)\mathrm{}}{M\left(0\right)\mathrm{}}$. The result confirms a prediction of Campbell correlating anomalous temperature dependence with excess residual resistivity of the alloy. Quantitative agreement with a local-moment model as well as with the Campbell model, however, is poor. Data for tungsten in nickel show no anomalous temperature dependence.