Measurement of the hyperfine anomaly between 187Os and 189Os.

Abstract

NMR and spin echo measurements were performed on dilute samples of $^{187}\mathrm{Os}$ and $^{189}\mathrm{Os}$ in Fe. The magnetic hyperfine splitting frequencies ${\ensuremath{\nu}}_{\mathit{M}}$=|g${\mathrm{\ensuremath{\mu}}}_{\mathit{N}}$${\mathrm{B}}_{\mathrm{HF}}^{(\mathrm{eff})}$/h| at 4.2 K were determined to be 111.17(1) and 371.00(5) MHz for $^{187}\mathit{Fe}$ and $^{189}\mathit{Fe}$, respectively. Taking into account the known magnetic moments, the hyperfine anomaly is deduced to be $^{187}\mathrm{\ensuremath{\Delta}}_{\mathrm{Fe}}^{189}$ = +0.0195(2), which is of opposite sign and much smaller than expected theoretically. \textcopyright{} 1996 The American Physical Society.