31P Nuclear Magnetic Resonance and 101Ru Nuclear Quadrupole Resonance Measurements of Filled Skutterudites GdRu4P12 and TbRu4P12

Filled skutterudites GdRu 4 P 12 and TbRu 4 P 12 exhibit antiferromagnetic ordering below 22 and 20 K, respectively. In TbRu 4 P 12 , an additional anomaly exists at around 10 K under a zero field; the origin of this successive transition might be related to multipole ordering. In order to determine the detailed magnetic properties of GdRu 4 P 12 and TbRu 4 P 12 , we performed zero-field 31 P nuclear magnetic resonance (NMR) and 101 Ru nuclear quadrupole resonance (NQR) measurements on them. The zero-field 31 P-NMR spectra indicate the occurrence of magnetic transition only at 22 K (GdRu 4 P 12 ) and 20 K (TbRu 4 P 12 ). We observed an anomalous temperature dependence of the spin–lattice relaxation rate 1/ T 1 just below 20 K and a small anomaly at around 10 K in the 101 Ru-NQR of TbRu 4 P 12 . The temperature dependence of 1/ T 1 also indicates that the nesting condition in the ordered states of GdRu 4 P 12 and TbRu 4 P 12 is poorer than that of SmRu 4 P 12 .

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