Emergence of Frustrated Short-Range Order above Long-Range Order in the S = 1/2 Kagome Antiferromagnet CaCu3(OD)6Cl2∙0.6D2O

We report on the low-energy dynamics in kagome antiferromagnet CaCu3(OD)6Cl2∙0.6D2O (Ca-kapellasite) as studied by use of 2D-NMR measurements. Previous 35Cl-NMR measurements revealed that nuclear spin–lattice relaxation rate (1/T1) shows two peaks at temperatures, T* = 7.2 K and Ts \( \simeq \) 25 K. While low-temperature peak is ascribed to critical fluctuations near long-range magnetic ordering, origin high-temperature has not been fully understood. From 1/T1 D sites OD groups (DOD), we find no Ts, evidencing related molecular groups. discuss possibility a frustration-induced short-range ordered state below before order stabilized Dzyaloshinskii–Moriya interaction. also observed static internal fields DOD site T*, confirm previously proposed negative-chirality q 0 structure.