Anisotropy-tuning by doping: phase diagram of CsNi 0.98Fe 0.02Cl 3 measured by caloric experiments

Abstract

The magnetic phase diagram of the Fe 2+ doped hexagonal ABX 3 compound CsNi 0.98Fe 0.02Cl 3 is investigated measuring the specific heat capacity and the magnetocaloric effect. In contrast to earlier specific heat, ultrasound and NMR experiments our measurements identify transitions between three ordered phases with the field applied in the hexagonal plane. Since the pure compound, a Heisenberg antiferromagnet with weak Ising anisotropy, has only two ordered phases for this field direction, while three are predicted for weak easy-plane anisotropy, our data provide the unambiguous proof that the anisotropy of CsNiCl 3 can be effectively modeled by doping with Fe 2+.