采用固相反应法制备La5/8（PrxCa1-x）3/8MnO3（x=0.25,0.5,0.75）多晶样品,研究其磁性质和电磁输运特性.X射线衍射表明,La5/8（PrxCa1-x）3/8MnO3（x=0.25,0.5,0.75）多晶样品室温的晶体结构呈Pnma空间群的正交结构.磁化强度-电阻（M～T）关系显示,La5/8（PrxCa1-x）3/8MnO3（x=0.25,0.5,0.75）的居里温度TC随Pr掺杂量增加而逐渐降低,三种样品分别为160K、150K、100K.此外,随着Pr3＋掺杂量增加,样品晶格畸变程度增大,铁磁相互作用减弱,并且三种成分均形成自旋玻璃态,其自旋冻结温度分别为150K、75K、70K.电阻-温度（ρ～T）关系表明,样品在x=0.25时出现电阻的双峰现象,这是由于样品中铁磁相与反铁磁相相互竞争造成的.结果表明,通过对钙钛矿锰氧化物的A位稀土掺杂,可对其CMR效应进行有效调控.
The magnetic and the electrical properties of polycrystalline Las/8 （Prx Ca1-x ）3/8 MnO3 prepared by solidstate reaction were investigated. X-ray diffraction （XRD） indicated that La5/8 （PrxCa3-x）1/8 has an orthorhombic type with pnma space group at room temperature. The temperature dependence of magnetization showed that the Curie temperature Tc decreased with decreasing the Pr concentration, and the Tc for La5/8 （Prx Ca1-x ）3/8 MnO3 （x= 0. 25,0. 5,0. 75） is around 160K, 150K, and 100K, respectively. Furthermore, upon increasing the Pra＋ concentration the degree of the lattice distortion increases, which weakens the ferromagnetic interaction and results in the spin glass state. The spin frozing temperatures of La5/8 （PrxCa1-x）3/8MnO3 （x=0. 25,0. 5,0. 75） are around 150K, 75K, and 7OK, respectively. The electrical resistance as a function of temperature showed that the phenomenon of doublepeak for x=0. 25 sample was observed, which is mainly due to the competition of ferromagnetic phase and anti-ferromagnetic phase. Magnetoresistance measurements indicated that the CMR could be modulated by the A-site doping in these compounds.
参考文献
| [1] | C. N. R. Rao;A. K. Cheetham .Charge Ordering in Manganates[J].Science,1997(5314):911-912. |
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