Nuclear-Magnetic-Resonance Studies ofMn55in Ni-Mn Alloys

The nuclear-magnetic-resonance line shapes of ${\mathrm{Mn}}^{55}$ have been studied in ferromagnetic Ni-rich Ni-Mn alloys with Mn concentrations of between 0.8 and 20.5 at.% Mn. Measurements were made at 4.2°K and over smaller concentration ranges at 77°K and room temperature by plotting the spin-echo amplitudes as a function of frequency across the inhomogeneously broadened nuclear resonance lines. Satellites are observed at low Mn concentrations at 4.2°K on both the high- and low-frequency sides of the dilute Mn in Ni line. A detailed analysis of the satellite structure is made by considering contributions to the hyperfine fields at the nuclei from the parent atom as well as from neighboring atoms, taking into account the antiferromagnetic interactions which exist in these alloys. In addition to the localized effects associated with the satellite structure, a shift of the dilute-Mn-in-Ni line is observed at low Mn concentrations which may be due to a long-range increase of moments on Mn atoms due to the addition of Mn. Studies made on a dilute (0.8 at.%) Mn-in-Ni alloy in external dc magnetic fields indicate the ${\mathrm{Mn}}^{55}$ hyperfine field to be negative.