作　　者： ; ; ;

机构地区： 天津大学理学院现代材料物理研究所

出　　处： 《金属学报》 2006年第9期974-978,共5页

摘　　要： 采用溶胶-凝胶法制备了(Pr_(1-x)La_x)_(0．75)Na_(0．25)MnPO_3(0．00≤x≤1．00)系列多晶样品．X射线衍射结果表明．所有样品均为单相类钙钛矿结构,随着La^(3+)离子含量的增加,样品由x≤0．50时的正交结构转变为x≥0．70时的菱面体结构．磁性测量结果表明,La^(3+)离子的掺入还导致了Pr_(0．75)Na_(0．25)MnO_3电荷有序的破坏．在x≤0．1时,电荷有序转变温度随La^(3+)离子含量增加而降低；当x＞0．10时,电荷有序现象消失,样品出现顺磁-铁磁相变,同时伴随着绝缘体-金属转变．磁熵变研究表明,x≥0．5的样品在室温附近和较低磁场下具有较大的磁熵变,可望成为新的室温磁致冷材料． Polycrystalline （Pr1-xLax）0.75Na0.25MnO3（0.00 ≤ x ≤ 1.00） manganites were prepared by sol-gel method. X-ray Diffraction patterns showed that the samples are crystallized in single phase with perovskite-like structure. The structure of the compounds transforms from orthorhombic structure for x≤0.50 to rhombohedral structure for x ≥0.70. The introduction of La^3＋ ions also suppresses the charge ordering in the samples. The charge ordering transition temperature decreases with increasing La^3＋ doping when x ≤0.10. The charge ordering phenomenon disappeared for the samples with x 〉 0.10, paramagnetic-ferromagnetic transition appeared, while the insulator-metal transition can be observed. For x≥0.50, the compounds also show large magnetic entropy change under low field near or above room temperature, indicating the material can he used in magnetic refrigeration.

关 键 词： 锰氧化物 庞磁电阻 电荷有序 相分离 磁熵变

领　　域： [理学] [理学] [一般工业技术]