Dimensional Crossover of Low-Energy Magnetic Excitation for Delafossite Oxide Cu1-xAgxCrO2 with a Spin-3/2 Antiferromagnetic Triangular Sublattice

Dimensional crossover from anisotropic-three-dimensional (3D) to 2D low-energy magnetic excitations was found in delafossite oxide Cu1-xAgxCrO2 having a spin-3/2 antiferromagnetic (AF) triangular lattice. The crossover is evidenced by a decrease in AF transition temperature (T-N), distinct 2D magnetic excitations above T-N for Cu0.85Ag0.15CrO2, a disappearance of a peak of magnetic specific heat (C-mag) around T-N, and a successive change from T-3 to T-2 dependence of low-T C-mag accompanying a low-T shift of magnetic entropy. These results may suggest a gradual change from AF to spin-liquid like states with an increase in x.