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-31m) form of manganese antimonite (MnSb
₂
O
₆
) was analyzed by means of the power-law relations with the critical exponent α in the vicinity of the Néel temperature of T
_N
= 8.0 K. While the extracted values of α from both f and C
_p
below T
_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
_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) λ of MnSb
₂
O
₆
was calculated from the pseudospin-phonon-coupled (PS) model and the energy fluctuation (EF) model below T
_N
. Our results are in good agreement with the data. In addition, the activation energy was calculated from the predicted values of λ from both PS and EF models for MnSb
₂
O
₆
. Our results indicate an order-disorder-type transition at T
_N
= 8.0 K for MnSb
₂
O
₆
.