A mean-field scaling method for first- and second-order phase transition ferromagnets and its application in magnetocaloric studies

We present a method based on mean-field theory, where from scaling of experimental magnetization data, the mean-field exchange parameter lambda and the f function of the equation of state M= f [(H + H-exch)/T] are directly determined. The scaling approach allows finding the dependence of Hexch on T or higher powers of M, which determine the order of the phase transition. Within the thermodynamics of the mean-field theory, the magnetocaloric effect is obtained, in a straightforward way, from the magnetic equation of state. Results are presented for first- and second-order magnetic phase transitions in manganites and metastable nanocrystalline metal alloy. (C) 2007 American Institute of Physics.