Dimensional Crossover of Low-Energy Magnetic Excitation for Delafossite Oxide Cu_1−xAg_xCrO₂ with a Spin-3/2 Antiferromagnetic Triangular Sublattice

Abstract

Dimensional crossover from anisotropic-three-dimensional (3D) to 2D low-energy magnetic excitations was found in delafossite oxide Cu_1−xAg_xCrO₂ 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 Cu_0.85Ag_0.15CrO₂, a disappearance of a peak of magnetic specific heat (C_mag) around T_N, and a successive change from T³ to T² 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.