Influence of Cr-Addition on Magnetic Properties and Magnetocaloric Effect of Fe-Cr-B-Gd-Zr Rapidly Quenched Alloys

Abstract

In this paper, the influence of Cr on structure, magnetic properties and magnetocaloric effect of Fe82−xCr4+xB2Gd2Zr10 (x\u2009=\u20091, 2, 3 and 4) alloy ribbons were investigated. The ribbons with a thickness of ∼\u200925 μm were prepared by using the melt-spinning method on a single roller system. x-ray diffraction analysis shows that the ribbons are almost amorphous. By changing the concentration of Cr from 5% to 8%, Curie temperature (TC) of the alloys reduces from 306 K to 282 K. Temperature dependence of magnetic entropy change, ΔSm(T), was calculated from magnetization versus magnetic curves, M(H), determined at various temperatures. With magnetic field change of 12 kOe, maximum magnetic entropy change of the alloy, |ΔSm|max, is larger than 0.8 J kg−1 K−1. Wide working temperature range (ΔTFWHM\u2009>\u200980 K) around room temperature has been achieved on these alloy ribbons, showing the high possibility of the alloy for practical application in magnetic refrigerators. By using Arrott–Noakes plots and Kover–Fisher method, critical analyses around the ferromagnetic–paramagnetic phase transition elucidated the magnetic orders in the alloys. The obtained critical parameters fall between those of the mean-field model and 3D Heisenberg model, indicating the coexistence of short-range and long-range ferromagnetic interactions in the alloy ribbons.