Critical Behaviour in the Specific Heat of an Antiferromagnet with Chiral Symmetry

Abstract

We report on high-resolution measurements of the specific heat, C, near the phase transition of CsMnxMg1-xBr3 in magnetic fields up to 6 T. In CsMnBr3 the critical exponent of the specific heat is found to be α = 0.40 ± 0.05 in excellent agreement with theoretical calculations for chiral-symmetry models. Upon dilution of CsMnBr3 with Mg the phase transition broadens and α strongly decreases towards α ≈ 0.2 for x = 0.95. For all investigated samples with different concentrations the critical behaviour remains unaffected by a magnetic field applied parallel to the c-axis, while a field perpendicular to c destroys the chiral symmetry.