Discrepancies in NMRON Knight Shifts of impurity nuclei in ferromagnets

Precision NMRON field shift studies have been carried out up to 8T on a⁵⁴MnNi single crystal along a hard 100] direction and on a¹²⁵SbFe single crystal along a hard 110] direction. For both systems, high field (B _app>-1T) and low field (0.3T<B _app<0.8T) data sets are obtained. The analysis reveals a significant discrepancy between the apparent Knight Shift dependent on whether the low field or high field data set is utilised. For both systems, consideration of the high field data sets yield a zero Knight Shift K(⁵⁴MnNi)=+0.0(0.2)% and K(¹²⁵SbFe)=+0.2(1.4)%, whereas the low field data sets yield K(⁵⁴MnNi)=+7.5(3.9)% and K(¹²⁵SbFe)=−5.4(3.3)% respectively. The field range dependence of K suggests that only Knight shifts measured in large fields (>-1T) are meaningful for establishing systematics. This casts some doubt on the greater bulk of the literature’s NMRON Knight shift studies, where predominantly low fields have been used to determine K.