Anisotropy-tuning by doping: phase diagram of CsNi0.98Fe0.02Cl3 measured by caloric experiments

The magnetic phase diagram of the Fe2+ doped hexagonal ABX(3) compound CsNi 0.98Fe0.02Cl3 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 ordere d phases with the field applied in the hexagonal plane. Since the pure comp ound, a Heisenberg antiferromagnet with weak Ising anisotropy, has only two ordered phases for this field direction. while three are predicted for wea k easy-plane anisotropy, our data provide the unambiguous proof that the an isotropy of CsNiCl3 can be effectively modeled by doping with Fe2+. 2001 El sevier Science B.V. All rights reserved.