Temperature dependence of the hyperfine fields of iron alloys

The distribution of hyperfine fields in three alloys of iron containing approximately 1 / 2 % of Co, Ni, Sn, has been measured by continuous wave NMR in the temperature range 4.2-400 K. A satellite line is observed in each distribution which is attributed to iron atoms with one impurity in the third nearest neighbour shell. The difference between the satellite line (normalized to 0 K) and pure iron at temperature T is found to be proportional to T 3/2 over the whole temperature range.