Nd_(1.85-x)R_xCe_(0.15)CuO_(4±δ)(R=Gd,Sm)单晶样品的红外光谱和超导转变关系的研究  

STUDY OF THE RELATIONSHIP BETWEEN THEFOURIER TRANSFORM INFRARED SPECTRA AND THE SUPERCONDUCTIVITY FOR THE Nd_(1.85-x)R_xCe_(0.15)CuO_(4±δ)(R=Gd and Sm) SINGLE CRYSTALS

作　　者：杨宏顺[1] 蒋成颍[1] 许祥益[1] 孙成海[1] 柯少秦[1] 冷荣军[1] 阮可青[1] 

机构地区：[1]中国科学技术大学物物理系,合肥230026

出　　处：《低温物理学报》2012年第6期430-435,共6页Low Temperature Physical Letters

摘　　要：研究了不同元素(Gd,Sm)掺杂和不同掺杂浓度的Nd1.85-xRxCe0.15CuO4±δ(R=Gd,Sm)单晶样品的X射线衍射、傅里叶变换红外光谱和电阻率.X射线衍射结果表明掺杂没有杂质峰,且峰的半高宽度很小,说明两掺杂体系的单晶样品品质很好.两体系晶格常数c均随着掺杂量的增加而降低,其中Gd掺杂体系的降低速率明显大于Sm.对于Gd掺杂,随着掺杂量的增加红外光谱逐渐向高频移动,而Sm掺杂红外光谱峰位几乎保持不变.这表明用Gd取代Nd会使Cu-O键变短,而用Sm取代Nd后Cu-O键键长几乎不变.电阻率的测量结果发现随着掺杂量的增加两体系的超导转变温度TC均被压制,载流子局域化效应均增强.而对于Gd掺杂,超导转变温度TC被更强烈的压制,载流子局域化效应更强,这一现象与两掺杂体系的晶胞体积的变化情况一致,也可能与和费米面上电子态密度随掺杂量的改变有关.The X-ray diffraction （XRD）, Fourier transform infrared （FTIR） spectra, and resistivity p are studied on Nd1.85-xRxCe0.15CuO4±δ（R=Gd,Sm） single crystals. The X-ray diffraction patterns of Nd1.85-xRxCe0.15CuO4±δ（R=Gd,Sm） single crystals show that there are no any impurity peaks in the experimental rang and the full width at half maximum （FWHM） are very small, which indicates that the samples are of high quality. The lattice constant c for Gd substitution decreases more sharply with increasing the doping concentration than that for Sm doping. The transmission peaks shift to high frequency for Gd doping but nearly unchanged for Sm doping, which indicates that substituting Nd with Gd will make the Cu-O distance short, while the Cu-O distance is nearly unchanged when we substitute Nd with Sm. The decrease of lattice constant c and the Cu-O distances make the volume of the unit cell V decrease more sharply for Gd doping than that for Sm doping, which in turn makes the electron density of states at EF decrease faster for Gd doping than that for Sm doping. The superconducting transition temperature Tc for Ndl. as x Gdx Ceo. 15 Nd1.85-xRxCe0.15CuO4±δ（R=Gd,Sm） systems are all suppressed with increasing the doping content. However, the superconducting Tc is strongly depressed {or Gd doping, and the Tc decrease slowly for Sm doping. This trend is very corresponding to the localization of charge carries, the change of the volume of the unit cells and possibly the change of density of states at EF mentioned above for two series.

关 键 词：电子型高温超导体 电子结构 红外光谱 

分 类 号：TM26[一般工业技术—材料科学与工程]