Charge fluctuation in S = 1/2 triangular lattice cluster antiferromagnets Li2ScMo3O8and Li2InMo3O8

We investigated macroscopic and microscopic physical properties of S = 1/2 Mo3 cluster magnets Li2ScMo3O8 and Li2InMo3O8. Li2InMo3O8 shows magnetic ordering at TN 12 K, while no magnetic ordering is observed down to 0.5 K in Li2ScMo3O8 in spite of the strong antiferromagnetic interaction among clusters probed by the Weiss temperature. 115In and 45Sc NMR measurements demonstrate that there should be difference in charge fluctuation in clusters between Li2InMo3O8 and Li2ScMo3O8. Our result suggests that the origin of different ground states realized in Li2InMo3O8 and Li2ScMo3O8 is different condition in charge and local structure as one of characteristics of the cluster magnet.