Mössbauer-effect study of a nearly homogeneousCr75Fe25alloy doped with 0.6 at.%Sn119

Using the Mössbauer effect at ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ and ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$ nuclei we study a ${\mathrm{Cr}}_{75}$ ${\mathrm{Fe}}_{25}$ alloy doped with 0.6 at.% ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$ in the temperature range of 4.2-331 K. We find that the sample, being chemically very homogeneous (>90%), is magnetically very heterogenous, i.e., it cannot be described with only one characteristic magnetic temperature contrary to expectation from the existing phase diagram. On a microscale it consists of a magnetic (M) and a nonmagnetic phase, the latter persisting down to $T\sim 9$ K. The contribution of the M phase increases discretely on lowering $T$. This permits the definition of characteristic temperatures $T_N^c$ at which Fe atoms having another $N$ Fe atoms in the first-neighbor shell become magnetic. At $T\sim 20$ K the average hyperfine field shows a steeper change with $T$ which may be indicative of a spin-freezing process expected to occur in that region.