Formation Ability And Magnetic Properties Of Gd_50-xCo₅₀?Ni,Fe?_x Amorphous Magnetocaloric Alloy

Magnetic refrigeration has the advantages of efficient energy saving,green environmental protection,etc.It is considered to be the most potential green refrigeration technology to replace gas compression refrigeration.The working efficiency of the refrigerator depends on the magnetocaloric characteristics of the magnetic working medium.Therefore,it is very important to develop new materials with excellent magnetocaloric effect.In this paper,the composition of alloys is designed based on Gd₅₀Co₅₀ amorphous alloy,combined with?^?9?criterion.This article is dedicated to improving the amorphous forming ability and magnetic properties of the Gd₅₀Co₅₀alloy.Firstly,the effect of Ni doping on the formation ability and magnetic properties of Gd₅₀Co₅₀ amorphous was studied.The?^?9?criterion used to predict the amorphous forming ability of Gd_50-xCo₅₀Ni_x?x=1,2,3?alloy.The XRD and DSC data show that Ni substitution for Gd can improve the amorphous forming ability of Gd₅₀Co₅₀ amorphous alloy,which is consistent with the predicted results.The Gd_50-xCo₅₀Ni_x?x=1,2,3?amorphous alloy exhibits typical secondary magnetic phase transition characteristics,and their Curie temperature?T_c?increases with increasing Ni content.1%Ni replaces Gd,the-?35?S_m^peakis significantly improved,but it gradually decreases as the Ni content continues to increase.The mechanism of the alloy's magnetocaloric properties decreasing with the increase of Ni content was verified by analyzing the change of effective magnetic moment.In addition,the peak field dependence of the magnetic entropy change of the alloy can be expressed by-?35?S_m^peak?Hⁿ,and the n value near the Curie temperature T_c obtained by the straight line fitting method is close to the theoretical predicted value.Secondly,the amorphous forming ability,the relationship between magnetic properties and microstructure of Gd-Co-Fe ternary alloy was studied.The?^?9?criterion predicts that the amorphous forming ability of the Gd_50-xCo₅₀Fe_x?x=1,2,3,4,5?alloy decreases with the increase of Fe,which is consistent with the experimental results.Fe replacing Gd improves the T_c of the alloy(Gd₄₈Co₅₀Fe₂ has a T_c up to 297K)while the-?35?S_m^peaksignificantly reduced.Gd₄₇Co₅₀Fe₃ and Gd₄₆Co₅₀Fe₄ exhibit the characteristics of multiphase transformation,which is mainly related to the nanoclusters and nanocrystalline phases present in their microstructures.After Fe replaced Gd,the n values of the alloys were all greater than 2/3,which confirmed the deviation of their magnetocaloric behavior from the average field prediction.Finally,the effect of Ni substitution for Gd on Gd₄₈Co₅₀Fe₂ amorphous alloy was studied.The amorphous forming ability decreases with increasing Ni content.As the content of Ni increases,the Curie temperature increases,-?35?S_m^peakdecreases,and?35?T_ad^peakincreases slightly first,and then decreases.When Ni replacement amount is 1%,?35?T_ad^peakreaches the maximum?3.95K?.After Ni replaces Gd,the local non-uniformity of the internal structure of the alloy makes the field-dependent parameter n value higher than the theoretically predicted average field value.