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

In this paper, the influence of Cr on structure, magnetic properties and magnetocaloric effect of Fe82-xCr4+xB2Gd2Zr10 (x = 1, 2, 3 and 4) alloy ribbons were investigated. The ribbons with a thickness of similar to 25 mu m 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 (T-C) of the alloys reduces from 306 K to 282 K. Temperature dependence of magnetic entropy change, Delta S-m(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, |Delta S-m|(max), is larger than 0.8 J kg(-1) K-1. Wide working temperature range (Delta T-FWHM > 80 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.