Magnetic anomaly in Ni51.5Fe21.5Ga27 single crystalline ferromagnetic shape memory alloy studied by ac impedance measurements

A magnetic anomaly in the austenitic state of Ni(51.5)Fe(21.5)Ga(27) single crystalline ferromagnetic shape memory alloy has been studied by means of ac impedance measurements. A much stronger effect of the degree of atomic order on the temperature of this anomaly (as compared to the temperature of the martensitic and para-ferromagnetic transitions) has been found. It has been shown that apart from the previously reported slight variation in the saturation magnetization, the magnetic anomaly results in a nearly one order of magnitude change in the value of initial magnetic permeability. The anomaly is not revealed in the resistive impedance at low frequencies, pointing likely to its purely magnetic origin. (C) 2009 American Institute of Physics. [DOI:10.1063/1.3106043]