Enhanced Curie Temperature and Critical Exponents of Fe‐Substituted NiCu Alloy

Abstract

The magnetic moment and the Curie temperature of the NiCu alloy decrease to a large extent with Cu. A Ni60Cu40 alloy with Fe substitutions up to 2 at% using a polyol‐mediated synthesis process resulting in enhanced magnetic properties is obtained. The Ni60Cu39Fe1 and Ni60Cu38Fe2 alloys show fcc phase with the Curie temperatures of 237 and 266 K, respectively. The room temperature magnetization measurement shows paramagnetic behavior, whereas, at 15 K, the 1 at% Fe‐substituted alloy exhibits a saturation magnetization of 20 emu g−1 that increases by 25% with 2 at% Fe. The positive slope in the Arrott plot confirms the second‐order phase transition in the alloys. The maximum magnetic entropy change (MCE) is observed as 0.101 J kg−1 K−1 for the Ni60Cu39Fe1 alloy with the peak temperature of 238 K in an applied magnetic field of 0.5 T. The critical exponent (β) calculated using the MCE method is in the range of 0.576(3)–0.587(3) for the alloys, whereas the values obtained using the Kouvel‐Fisher (KF) method are 0.523(3)–0.565(2). The extracted β values are slightly greater than the mean‐field model suggesting clustering behavior in the alloys.