Nuclear-Magnetic-Resonance Studies ofMn55in OrderedNi3Mn

Nuclear-magnetic-resonance studies of ${\mathrm{Mn}}^{55}$ as well as bulk magnetization measurements have been carried out on ${\mathrm{Ni}}_3$Mn samples having various degrees of order. The results are interpreted in terms of long-range-ordering theory and neighbor contributions to the hyperfine fields. A theoretical expression for the magnetization as a function of order is given, which is valid for values of the long-range-order parameter $S$ in the range 0.6-1.0. An NMR line at -370 kG is identified with ${\mathrm{Mn}}^{55}$ in a well-ordered environment. Other lines are attributed to incompletely ordered sites. Consideration of the difference between the resonance of the well-ordered Mn and that of dilute Mn in Ni leads to values for next-nearest-neighbor as well as nearest-neighbor effects on the hyperfine field. The effect of temperature on the spectra is attributed, in part, to average exchange interactions being different for different environments.