Gd4（Bi,Ge）3化合物的室温磁熵变效应（英文）

Room temperature magnetocaloric effect of Gd4（Bi,Ge）3 compound

通过电弧熔炼和随后的退火处理制备出单相多晶化合物Gd4Bi3-xGex(x=0,1和2)。Gd4Bi3-xGex的晶体结构为反Th3P4型,空间群为I-43d。晶胞参数a从x=0的0.939 93(2)nm减少到x=2的0.906 97(2)nm。通过Arrott方法得到x=0,1和2的居里温度分别为327、350和296 K。5 T变场下,x=0,1和2的最大磁熵变分别为2.7、2.3和3.4 J·kg^-1·K^-1,相对制冷能力分别为257、184和442 J·kg^-1。居里温度附近的临界磁行为遵循标度理论。居里温度之上和之下的等温磁化曲线可用两个不同的正则函数描述。分析表明,Gd4BiGe2在铁磁-顺磁转变附近的磁行为为平均场下的长程相互作用。

The phase pure Gd4Bi3-xGex(x=0,1 and 2)polycrystalline compounds were prepared by arc melting and subsequent annealing.Gd4Bi3-xGex adopts the cubic anti-Th3P4 structure(space group I-43d),and its lattice parameter a decreases from 0.939 93(2)nm of x=0 to 0.906 97(2)nm of x=2.The Curie temperature TC is respectively 327,350 and 296 K respectively for x=0,1 and 2 determined by the Arrott method.Gd4Bi3-xGex has the maximum magnetic entropy change of 2.7,2.3 and 3.4 J·kg^-1·K^-1 and the relative cooling power of 257,184 and 442 J·kg^-1 for x=0,1 and 2,respectively,around TC in a field induction variation of 5 T.The critical magnetization behavior near TC follows the scaling theory,and the field dependence of magnetization can be described as two distinct regular functions above and below TC.Long range magnetic interactions dominate the magnetization behavior of Gd4BiGe2 in the vicinity of ferromagnetism-paramagnetism transition in the mean field model.