Phenomenological Study of Manganese Antimonite Close to the Néel Temperature

The anomalous behavior of the frequency f and specific heat {C_p} data for the new layered trigonal (P\bar{3}1m) form of manganese antimonite (MnSb 2 O 6 ) was analyzed by means of the power-law relations with the critical exponent \alpha in the vicinity of the Néel temperature of {T_{\rm{N}}}= 8.0 K. While the extracted values of \alpha from both f and {C_p} below T_{\rm{N}} (the same value of 0.06) match exactly the value 1/16 (= 0.06) predicted from the three-dimensional (3-D) Ising model, the extracted value of 0.65 from the {C_p} data above T_{\rm{N}} is much higher than the predicted value of 1/8 (= 0.13) from the 3-D Ising model. As an extension of this work, the temperature dependence of the muon-spin relaxation rate (damping constant) \lambda of MnSb 2 O 6 was calculated from the pseudospin-phonon-coupled (PS) model and the energy fluctuation (EF) model below T_{\rm{N}}. Our results are in good agreement with the data. In addition, the activation energy was calculated from the predicted values of \lambda from both PS and EF models for MnSb 2 O 6 . Our results indicate an order-disorder-type transition at T_{\rm{N}}= 8.0 K for MnSb 2 O 6 .