Low Temperature Study of the Co1−xFexSi Alloys

A study of the internal magnetic field at the Co nucleus in Co1−xFexSi alloys was carried out at low temperatures using nuclear orientation techniques. Radioactive 57Co vas diffused into the samples and the anisotropy of the 14.4 KeV γ‐ray was observed at temperatures in the region of 40 mK. In the ferromagnetic region (x = 0.2 to 0.8) no detectable nuclear orientation was observed, thus placing an upper limit to the internal magnetic field at the 57Co nucleus of 50 kG. We have also carried out Mossbauer measurements at low temperature in the above samples. It was observed that the field at the 57Fe nucleus is very small, around 20 kG. These results seem to indicate that the ferromagnetism in these alloys is itinerant. This is in agreement with the spin echo measurements of Kawarazaki, et al.1 Our measurements have been extended also to the paramagnetic region (x below 0.2).