Oblique triangular antiferromagnetic phase in CsCu1-xCoxCl3 - art. no. 224425

The spin-1/2 stacked triangular antiferromagnet CsCu1-xCoxCl3 with 0.015<x< 0.032 undergoes two phase transitions at zero field. The low-temperature ph ase is produced by doping a small amount of Co2+. In order to investigate t he magnetic structures of the two ordered phases, the neutron elastic scatt ering experiments have been carried out for the sample with x approximate t o 0.03. It is found that the intermediate phase is identical to the ordered phase of CsCuCl3, and that the low-temperature phase is an oblique triangu lar antiferromagnetic phase in which the spins form a triangular structure in a plane tilted from the basal plane. The tilting angle, which is 42 degr ees at T=1.6 K decreases with increasing temperature, and becomes zero at t he lower transition temperature T-N2 = 7.2 K. An off-diagonal exchange term is proposed as the origin of the oblique phase.