Gd_(50)Co_(50)–xFe_(x)(x=7,10)非晶合金的近室温平台型磁热性能

Near room temperature table-like magnetocaloric properties in GdCoFe(x=7,10)amorphous alloys

采用熔体旋淬法制备了Gd_(50)Co_(50)–xFe_(x)(x=7,10)非晶合金条带,通过X射线衍射仪(XRD)、高分辨透射电子显微镜(HRTEM)、小角X射线散射(SAXS)、差示扫描量热仪(DSC)分析了样品的结构和热性能,采用综合物性测试系统(PPMS)测试了磁性能及磁热性能。结果显示,试样的组织结构和化学成分都是均匀的。结合已报道的数据,总结出对于Gd_(50)Co_(50)–xFe_(x)(x=0,2,5,7,10)系列非晶合金,其居里温度(TC)和最大磁熵变值(|ΔSMpk|)分别随着Fe含量增加而升高和降低。在磁场变μ_(0)ΔH=5 T时,Gd_(50)Co_(43)Fe_(7)和Gd_(50)Co_(40)Fe_(10)分别在230~305 K和210~315 K温度区间获得磁熵变值为3.14±0.16 J/(kg·K)和2.76±0.14 J/(kg·K),展现出平台型磁热效应,这表明它们是适用于近室温埃里克森循环的磁制冷工质。另外,Fe元素添加增强了过渡金属(Fe和Co)亚晶格中的反铁磁或散铁磁相互交换作用,使合金具有散亚铁磁性,从而导致TC随着磁场的增强向低温偏移。

The Gd_(50)Co_(50)–xFe_(x)(x=7,10)amorphous ribbons were fabricated by single-roller melt-spinning method,and the microstructure,as well as the thermal,magnetic and magnetocaloric properties of the samples were detected by X-ray diffractometer,high-resolution transition electron microscopy,small angle X-ray scatterometer,differential scanning calorimeter and physical property measurement system.It was shown that the as-spun samples were microstructural and chemical homogeneous.Combined with the reported data of Gd_(50)Co_(50)–xFe_(x)(x=0,2,5)amorphous alloys,it can be found that with increasing Fe content,the Curie temperature TC increases and the maximum magnetic entropy change|ΔSMpk|decreases in the series of Gd_(50)Co_(50)–xFe_(x)(x=0,2,5,7,10)amorphous alloys.Moreover,the magnetocaloric effect tends to be table-like,and the|ΔSM|of 3.14±0.16 J/(kg·K)and 2.76±0.14 J/(kg·K)were observed in temperature ranges of 230-305 K and 210-315 K under the magnetic field change of 5 T for Gd_(50)Co_(43)Fe_(7)and Gd_(50)Co_(40)Fe_(10)amorphous alloys respectively,which make them attractive as magnetic refrigerant candidates working for Ericsson-cycle at near room temperature.Besides,the TC shifts to lower temperature under higher magnetic field.This phenomenon is probably owing to the sperimagnetism of the alloys,which is derived from the enhancement of antiferromagnetic or asperomagnetic interaction in the transition metal(i.e.Fe and Co in this work)sublattice by Fe addition.