Gd_(1-x)Ho_xCo_2的结构及磁热效应
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摘要
通过真空电弧熔炼的方法制备了Gd_(1-x)Ho_xCo_2(x=0,0.2,0.4,0.6)系列化合物,利用XRD、SEM、VSM等分析设备对其结构及其磁性能进行了研究。结果表明,Gd_(1-x)H_xCo_2系列化合物保持纯MgCu_2类型的Laves相结构,并存在在少量的GdCo_3相。该系列化合物的居里温度随着Ho含量的增加从399 K降低到了236K,降低幅度达到了67%,但在5T外场下磁熵变从3.3J/(kg·K)增加到了4.0J/(kg·K),变化幅度不大,说明Ho元素的替代在不改变磁熵变大小的同时可以有效地调节居里温度。另外还发现该化合物在5T外场下的制冷量随着Ho含量的增加从158.3J/kg增加到了254.6J/kg,增加了60.8%。也讨论了晶体结构和磁性能之间的变化规律,为进一步调节磁性能奠定基础,使得这类材料在宽温区范围内的实际应用更有竞争力。
Gd_(1-x)Ho_xCo_2(x=0,0.2,0.4,0.6)compounds were prepared by vacuum arc melting.The structure and magnetic properties for all samples were investigated using XRD,SEM and VSM.The results show that the Gd_(1-x)H_xCo_2 series compounds remain pure MgCu_2 type Laves phase structure,but there exist impurity phase GdCo_3 in the sample.With the increase of Ho contents,although the Curie temperature TCdecreases from 399 to 236Kby 67 percent,magnetic entropy changeΔSMincreases slightly from 3.3 to 4.0J/(kg·K)under 5T.The measurement results show that the substitution of Ho for Gd is effective methods to tune the Curie temperature while keeping the values of magnetic entropy change.Furthermore,The RC values increase from 158.3 to 254.6J/kg by 60.8% with increasing of Ho contents under 0-5T magnetic field.Furthermore,it is discussed about the relationship between the crystal structure and magnetic properties.Thus,it makes these materials more competitive for practical application in wide temperature regions.
Gd_(1-x)Ho_xCo_2(x=0,0.2,0.4,0.6)compounds were prepared by vacuum arc melting.The structure and magnetic properties for all samples were investigated using XRD,SEM and VSM.The results show that the Gd_(1-x)H_xCo_2 series compounds remain pure MgCu_2 type Laves phase structure,but there exist impurity phase GdCo_3 in the sample.With the increase of Ho contents,although the Curie temperature TCdecreases from 399 to 236Kby 67 percent,magnetic entropy changeΔSMincreases slightly from 3.3 to 4.0J/(kg·K)under 5T.The measurement results show that the substitution of Ho for Gd is effective methods to tune the Curie temperature while keeping the values of magnetic entropy change.Furthermore,The RC values increase from 158.3 to 254.6J/kg by 60.8% with increasing of Ho contents under 0-5T magnetic field.Furthermore,it is discussed about the relationship between the crystal structure and magnetic properties.Thus,it makes these materials more competitive for practical application in wide temperature regions.
引文
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[2]Brück E,Tegus O,Li X W,et al.Magnetic refrigeration towards room-temperature applications[J].Physica B,2003,327:431-437.
[3]Pecharsky V K,Gschneidner,Jr K A.Giant magnetocaloric effect in Gd5(Si2Ge2)[J].Phys Rev Lett,1997,78(23):4494-4496.
[4]Hu F X,Shen B G,Sun J R,et al.Influence of negativelattice expansion and metamagnetic transition on magnetic entropy change in the compound LaFe11.4Si1.6[J].Appl Phys Lett,2001,78:3675-3677.
[5]Tegus O,Brück E,Buschow K H J,et al.Transitionmetal-based magnetic refrigerants for room-temperature applications[J].Nature,2002,415:150-153.
[6]Wada H,Morikawa T,Taniguchi K,et al.Giant magnetocaloric effect of MnAs1-xSbxin the vicinity of first-order magnetic transition[J].Physica B Condensed Matter,2003,328:114.
[7]Thorsten Krenke,EyüpDuman,Mehmet Acet,et al.Inverse magnetocaloric effect in ferromagnetic Ni-Mn-Sn alloys[J].Nature Materials,2005,4(6):450-454.
[8]Wu Wei,LiuXiaolie,et al.Materials for magnetic refrigeration at ambient temperature and their applications[J].Rare Metal Materials and Engineering,2001,30(3):166-168.
[9]Zhong Xichun,Zeng Dechang,Liu Zhengyi,et al.Structure,magnetic properties and magnetic entropy changes of room temperature magnetic refrigeration alloys Pr2Fe17-xCox[J].Rare Metal Materials and Engineering,2005,34(10):1537.
[10]Han Zhida,Chen Jie.The phase transition and magnetocaloric effect in Dy(Co1-x Mnx)2 alloys[J].Journal of Changshu Institute of Technology,2011,(4):23-26.
[11]Gu Kunming,Li Junqin,Ao Weiqin,et al.The Influence of boron on the formation and magnetocaloric effect of DyCo2alloy[C]//Beijing:The 13th National Symposium on Phase Diagrams China-Japan Joint Symposium on Phase Diagrams,Materials Design and Their Applications,2006:474-477.
[12]Kim Anh D T,Thuy N P,Duc N H.Magnetism and magnetocaloric effect in La1-y Ndy(Fe0.88Si0.12)13 compounds[J].Journal of Magnetism and Magnetic Materials,2003,262(3).
[13]Hui Han,Lei Zhang,Zhu Xiangde,et al.Critical phenomenon in the itinerant ferromagnet Cr11Ge19studied by scaling of the magnetic entropy change[J].Journal of Alloys and Compounds,2016,693:389-393.
[14]Gschneidner K A Jr,Pecharsky V K,Pecharsky A O,et al.Recent developments in magnetic refrigeration[J].Mater Sci Forum,1999,315-317:69.
[15]Zhong X C,Gao B B,Liu Z W,et al.Amorphous and crystallized(Gd4Co3)100-xBx alloys for magnetic refrigerants working in the vicinity of 200K[J].Journal of Alloys&Compounds,2013,553(6):152-156.
[16]Zheng Z G,Tan Z C,Yu H Y,et al.Structural,magnetic properties and magnetocaloric effect of Mn1.2Fe0.8P1-x SixB0.03compounds[J].Materials Research Bulletin,2016,77:29-34.