Nuclear Magnetic Resonance in Ferromagnetic Fe2P

Abstract

The NMR of 31P and 57Fe has been studied in Fe2P using a pulsed spectrometer. Resonances have been observed at frequencies 17.5, 20, 77.5, and 86.6 MHz allowing the deduction of the hyperfine fields at the various atomic sites. These are Hn(Fe I) = 148 kOe, Hn(Fe II) = 123 kOe, Hn(P I) = 50.2 kOe, and Hn(P II) = 45.0 kOe. From the shift in the NMR frequency on application of an external magnetic field, the sign of the phosphorus hyperfine fields is shown to be positive. The temperature dependence of the 31P NMR frequency has also been studied and the data is well fitted by a T2 law. Domain-wall enhancement is investigated in the light of a pinned-membrane model. Finally nuclear 31P and 57Fe spin relaxation times are measured. The longitudinal relaxation is due to thermally driven domain-wall motions, and this mechanism also produces the transverse relaxation at high temperatures, although at low temperatures spin-spin coupling is evident.