Nuclear orientation and Mössbauer studies of alloys of CoSi-FeSi

The hf magnetic field at the Co nucleus in ${\mathrm{Co}}_{1-x}{\mathrm{Fe}}_x\mathrm{Si}$ alloys was measured at low temperature using nuclear-orientation techniques. Radioactive ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ was diffused into the samples and the anisotropy of the 14.4-keV $\gamma$ ray was observed at 26 mK. From this anisotropy, the hf field at the Co site was calculated: for $x=0.13\mathrm{}$, a value between 295 and 326 kOe was obtained; for $x=1\mathrm{}$ (${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ in FeSi), the hf field was 115 ± 15 kOe. Using the Mössbauer effect, no detectable hf magnetic field was observed at the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ nucleus for $x=0.13\mathrm{}$ as well as $x=1\mathrm{}$. This agrees with the suggestion that the magnetic moment in ${\mathrm{Co}}_{1-x}{\mathrm{Fe}}_x\mathrm{Si}$ alloys is developed at the Co site. By measuring the change in the Mössbauer spectra caused by the application of an external magnetic field, the hf fields at the Fe nucleus in ferromagnetic samples of this alloy, $x=0.5\mathrm{} \mathrm{and} 0.7$, were calculated to be -22 ± 4 and -10 ± 4 kOe, respectively.