Nuclear Magnetic Resonances of Mn⁵⁵ and P³¹ in Ferromagnetic and Antiferromagnetic MnP

The zero-field nuclear resonances of Mn 55 and P 31 have been observed in both the ferromagnetic and antiferromagnetic (screw-spin) states of MnP. In the ferromagnetic state remarkably asymmetric resonance lines are observed. It is shown by using single crystal specimens as well as powder ones that all the resonances are enhanced by domain wall motion. The line shapes are analysed by taking account of the variation in the hyperfine field, electric quadrupole splitting and enhancement factor of the r f field across the domain wall. In the screw-spin state weak resonance lines having asymmetric shapes similar to those in the ferromagnetic state are observed. The line shapes are also interpreted on the basis of the screw-spin arrangement obtained by the neutron deffraction study. Anomalous changes in the resonance frequencies occur at 47°K, which corresponds to the temperature of the ferro-antiferromagnetic transition.