Specific heat and critical behaviour of CsMnI3

The authors report on measurements of the specific heat, C, of the triangular lattice antiferromagnet CsMnI 3 in the vicinity of the two successive phase transitions at T N1 =11.28 K and T N2 =8.19 K and in magnetic fields up to 6 T applied perpendicular to the c axis. Near T N2 the data can be fitted with a critical exponent alpha =-0.05+or-0.15 for B=0 compatible with the prediction of three-dimensional ordering with XY symmetry for this transition. Within the experimental uncertainty, the critical behaviour is not affected by a magnetic field.