Appearance of successive phase transition in SmRU4P12 under high magnetic fields probed by 31P nuclear magnetic resonance

The P-31-NMR (nuclear magnetic resonance) measurements of the filled skutterudite SmRu4P12 have been carried out in several applied magnetic fields. The line width of the P-31-NMR spectrum rapidly increases below the metal-insulator transition temperature T-MI, which indicates the appearance of an internal field below the temperature. Though no distinct anomaly was observed below T-MI in low fields, a complicated structure was observed between the Neel temperature T-N and T-MI (T-N < T-MI) above 70 kOe. The spin-lattice relaxation rate l/T-1 is almost independent of temperature above T-MI, and rapidly decreases below T-MI. The l/(T1) in low fields decreases monotonously, whereas the strong suppression of l/(T1) occurs between T-N and T-MI above 70 kOe. The structure of the spectra and the suppression of l/T-1 become apparent with increasing field.