Microscopic evidence for magnetic ordering in NdCu3Ru4O12: 63,65Cu nuclear quadrupole resonance study

We have conducted 63,65Cu nuclear quadrupole resonance (NQR) measurements on A-site ordered perovskite compounds LaCu3Ru4O12 and NdCu3Ru4O12 to investigate their ground state and spin fluctuations. While there is only one Cu site in the crystal structure, multiple NQR resonance lines were observed. This is presumed to be due to the presence of slight distortion and lattice defects in the samples. The nuclear spin-lattice relaxation rate divided by temperature, 1/T1T, for LaCu3Ru4O12 showed almost constant value indicating the Fermi-liquid state. A remarkable increase in 1/T1T due to spin fluctuations was observed in NdCu3Ru4O12. Furthermore, an evident magnetic phase transition at TM=0.6 K was revealed from the distinct peak of 1/T1T and the broadening of the NQR spectrum.