Unconventional critical behavior in the weak ferromagnet BaIrO3

We report the results of ac/dc magnetization study of the critical behavior in a weak ferromagnet BaIrO3. The critical temperature has been determined to be T-c = 182.8 K by the ac susceptibility measurement. We have analyzed our dc magnetization data near Tc with the help of the modified Arrott plot method. The critical exponents have been determined to be beta = 0.82 +/- 0.03, gamma = 1.03 +/- 0.03, and delta = 2.20 +/- 0.01, which roughly obeys delta = gamma/beta + 1. Using these values of T-c, beta, and gamma, we find that each magnetization-field-temperature (M-H-T) behavior below and above T-c obeys a scaling relation, following a single equation of state in which M/vertical bar epsilon vertical bar(beta) is uniquely related to H/vertical bar epsilon vertical bar((gamma+ beta)) where epsilon = (T - T-c)/T-c. These findings demonstrate that the ferromagnetic transition in BaIrO3 belongs to a new universality class of the second-order phase transition. Copyright (c) EPLA, 2008