(La_(0.9)Dy_(0.1))_(2/3)Ba_(1/3)Mn_(1-x)Al_xO_3(x=0,0.05)氧化物的结构与磁性

Structure and Magnetic Properties of (La_(0.9)Dy_(0.1))_(2/3)Ba_(1/3)Mn_(1-x)Al_xO_3(x=0,0.05) Oxides

【目的】为改善(La_(0.9)Dy_(0.1))_(2/3)Ba_(1/3)Mn_(1-x)Al_xO_3的磁热性能,研究掺杂Al对其晶体结构、居里温度、相变类型以及磁热性能的影响。【方法】采用固相反应法制备锰氧化物(La_(0.9)Dy_(0.1))_(2/3)Ba_(1/3)Mn_(1-x)Al_xO_3(x=0,0.05)样品,利用X射线衍射法分析样品的结构,用振动样品磁强计测量样品的磁性。【结果】所制备样品均为单相钙钛矿结构,属于菱方晶系,空间群为R-3c(No.167)。掺杂Al使样品居里温度由无掺杂的274K降低到248K,在外加磁场变化为20kOe时最大磁熵变由2.16J/(kg·K)降低到1.85J/(kg·K)。样品的铁磁-顺磁相变属于二级相变。采用双交换作用机制解释了居里温度和磁化强度的变化。【结论】非磁性元素Al替代Mn不改变其晶体结构,稍微降低了锰氧化物的磁热性能。

【Objective】The effects of Al doping on crystal structure,Curie temperature,phase change type and magnetocaloric properties of(La_(0.9)Dy_(0.1))_(2/3)Ba_(1/3)Mn_(1-x)Al_xO_3 were studied in order to improve its magnetocaloric properties.【Methods】The manganese oxides(La_(0.9)Dy_(0.1))_(2/3)Ba_(1/3) samples were prepared by the solid state reaction method.The structures of the samples were analyzed by X ray diffraction,and the magnetic properties of the samples were measured by the vibrating sample magnetometer.【Results】The prepared samples were single-phase perovskite structure,belonging to rhombic system,and the space group was R-3 c(No.167).With the doping of Al the Curie temperature decreased from 274 Kto 248 K,and the maximum magnetic entropy change decreased from 2.16 J/(kg·K)to 1.85 J/(kg·K)under an applied field change of 20 kOe.The ferromagnetic-paramagnetic transition in the samples belonged to the second order phase transition.Double exchange mechanism was used to explain the change of Curie temperature and magnetization.The changes of Curie temperature and the magnetization were explained by the double exchange mechanism.【Conclusion】The doping of nonmagnetic element Al at the Mn site did not change its crystal structure and slightly reduced the magnetocaloric properties of the manganese oxides(La_(0.9)Dy_(0.1))_(2/3)Ba_(1/3)Mn_(1-x)Al_xO_3.