NMR studies of ordered structures and valence states in the successive valence-transition system EuPtP

We have studied EuPtP, which undergoes two successive valence transitions at TA∼240 K and TB∼200 K by P31-nuclear magnetic resonance (NMR) measurements. From the analysis of NMR spectra, we obtained plausible ordered structures and Eu valence states in three phases divided by TA and TB. These ordered structures well explain observed inequivalent P sites and the intensity ratio of the NMR spectra arising from these P sites. The results are also in good accordance with mean Eu valence measured by the x-ray absorption spectroscopy. We also discuss Eu 4f states and the origin of the transitions from the measurements of nuclear spin lattice relaxation rate and hyperfine coupling constant.