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1.
采用脉冲激光沉积方法,在SrTiO3(STO)基片上原位制备了电子型掺杂高温超导体La1.89Ce0.11CuO4(LCCO)与超大磁电阻(CMR)材料La0.7Ca0.3MnO3(LCMO)异质结.使用X射线衍射和透射电镜分析,表明异质结是c轴取向外延生长.LCCO层的超导转变温度TC0是18.5K,LCMO层的金属-绝缘转变温度为195K.我们研究了这种异质结的界面微分电导,得到LCCO的能隙大小是4.2meV.  相似文献   

2.
本文中采用脉冲激光沉积的方法原位制备了结构完整的La1.89Ce0.11CuO4(LCCO)/Ba0.7Sr0.33TiO3(BST)/La0.67Sr0.33MnO3(LSMO)三层膜,并在此基础上制得了类似P-I-N型的全钙钛矿结构材料异质结.在不同的温度区间对其电输运性质进行了测量.测量结果表明随着充当绝缘层的Ba0.7Sr0.3TiO3的厚度的变化,异质结的电输运机制也在变化.当其厚度到达25纳米时,整个结在低温区呈现良好的整流特性.  相似文献   

3.
用高分辨电镜观察了室温下La1.48Nd0.4Sr0.12CuO4和La1.88Sr0.12CuO4样品的原子结构像,观察到了其中的La2O2层和CuO2层沿c轴方向交叉堆砌.这两个样品的微结构非常相似,说明Nd掺杂没有造成周期性的调制结构.用变温X射线研究了La1.48Nd0.4Sr0.12CuO4样品中低温正交(LTO)到低温四方(LTT)结构相变,给出了晶格常数随温度的演化过程.  相似文献   

4.
赵昆  黄康权 《低温物理学报》2003,25(Z2):415-419
本文用对靶溅射技术制备了La2/3Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3薄膜.与YBCO单层薄膜相比,由于超导/铁磁系统中的磁性邻近效应,三层薄膜表现出较低的超导转变温度.薄膜的R~T测量曲线显示出超磁阻(CMR)效应和超导转变,预示着超导和铁磁特性共存于LCMO/YBCO/LCMO三文治结构.  相似文献   

5.
The perovskite bilayers La0.67Ca0.33MnO3 (LCMO) (100 nm) / La0.67Sr0.33MnO3(LSMO) (100 nm) and LSMO (100 nm) / LCMO (100 nm) are fabricated by a facing-target sputtering technique. Their transport and magnetic properties are investigated. It is found that the transport properties between them are different obviously due to distinguishable structures, and the different lattice strains in both films result in the difference of metal-to-insulator transition. Only single-step magnetization loop appears in our bilayers from 5K to 320K, and the coercive force of LSMO/LCMO varies irregularly with a minimum ~ 2387A/m which is lower than that of LCMO and LSMO single layer films. The behaviour is explained by some magnetic coupling.  相似文献   

6.
利用脉冲激光沉积技术在掺Nb的SrTiO3衬底上制备了氧非正分La0.9Ba0.1MnO3-δ/SrTiO3:Nb p-n异质结.在20-300 K这一较宽的温度范围内获得了光滑的整流曲线.整流实验表明:该p-n异质结的正向扩散电压V0随着温度升高在薄膜金属-绝缘转变温度附近出现极大值,表现出与氧正分La0.9Ba0.1MnO3-δ/SrTiO3:Nb p-n结截然不同的温度特性.结合薄膜的电阻-温度实验和能带计算结果,对这一奇异的现象进行了解释.  相似文献   

7.
对La5/8-xPrxCa3/8MnO3(x=0,0.13,0.20,0.25)体系的电输运特性进行了系统研究.结果表明随着Pr含量的增大金属一绝缘转变温度(TMI)减小,在高于TMI的温度区域,该体系的电输运行为具有绝缘体特性,符合可变程跳跃模型;而在较低温度(50K以下),其电阻率存在极小值现象,且随磁场的增大而逐渐受到抑制.对这种电阻率极小值现象从强电子-电子相互作用角度进行了分析讨论.  相似文献   

8.
采用燃烧法合成了La1.6(MoO4)3∶Eu3+0.4纳米晶末,研究了其声子-掺杂-晶格相互作用和发光性质。 X射线粉末衍射(XRD)分析表明,在500~900℃退火后,La1.6(MoO4)3∶Eu3+0.4样品为单一晶相。对样品进行了光致发光(PL)测量,激发Mo6+-O2-电荷迁移带,观察到Eu3+的系列发光,表明Mo6+-O2-带和Eu3+间存在能量传递,中心波长分别在λ1=469 nm和λ2=426 nm处的两个one-phonon边带,相应的声子能量分别为767和1202 cm-1,分别对应于Mo O和Mo—O—Mo伸缩振动。同时,计算了两个局域模电子-声子耦合强度的黄昆因子分别为S1=0.055和S2=0.037,为揭示其三价离子高传导特性及其负热膨胀物理特性提供了实验基础。  相似文献   

9.
本文简要介绍对La0.5Er0.2Ca0.3Mno3进行低温电磁测量的实验过程,研究掺杂后复合体系的磁电阻效应。  相似文献   

10.
我们报告稀土化合物La3Co的单晶样品在不同的磁场中的电阻率随温度变化的测量结果,从而得出该材料的超导转变温度随磁场的变化关系,超导转变温度随磁场的增大而降低.我们认为这是由于磁场的加大使电子间的相互作用增强,同时减弱了材料中的有效电子(3d、4f)的转移作用.  相似文献   

11.
本文研究了La1-xNaxMnO3和La1-xAgxMnO3结构、磁性、电输运等.特别是研究了La0.8Na0.2MnO3的内耗特性.XRD研究发现La1-xNaxMnO3和La1-xAgxMnO3的结构均为R3C,但是不同的是对于La1-xAgxMnO3,当x>0.25时有Ag单质吸出.从磁化强度随温度的变化看出所有的样品都在室温或室温以上有顺磁到铁磁的转变,而且随着掺杂量的增加,居里温度也在增加.电输运研究发现对于La1-xNaxMnO3,x=0.15的电阻率最小,随掺杂量增大电阻率增大;x≥0.15的样品中存在电阻双峰.而对于La1-xAgxMnO3电阻率随掺杂量增加而减小;x<0.2的样品中存在电阻双峰.在La0.8Na0.2MnO3的内耗测量中发现了具有相变峰特征的内耗双峰.我们认为这种电阻双峰和内耗双峰来源于样品中存在A位空位,导致了样品中存在电子相和磁相的不均匀,即相分离.就是在样品存在着铁磁相和反铁磁相共存.  相似文献   

12.
The X-ray emission from 85 to 150 MeV Xe and 115 MeV La bombardments of thick natural La targets has been measured. The spectra and yields of X-ray emission are obtained. Continuous X-ray distributions have been found to lie beyond the target and projectile characteristic X-ray energies. The high-energy parts of these continua are interpreted as K-radiation of quasi-molecules with effective atomic numbers Z = 111 and Z = 114, respectively.  相似文献   

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16.
Mengwu Huo 《中国物理 B》2022,31(10):107401-107401
Superconductivity has been realized in films of La1-xSrxNiO2. Here we report synthesis and characterization of polycrystalline samples of La1-xSrxNiO3 and La1-xSrxNiO2 (0 ≤ x ≤ 0.2). Magnetization and resistivity measurements reveal that La1-xSrxNiO3 are paramagnetic metal and La1-xSrxNiO2 exhibit an insulating behavior. Superconductivity is not detected in bulk samples of La1-xSrxNiO2. The absence of superconductivity in bulk La1-xSrxNiO2 may be due to the generation of hydroxide during reduction, a small amount of nickel impurity, or incomplete reduction of apical oxygen. The effect of interface in films of La1-xSrxNiO2 may also play a role for superconductivity.  相似文献   

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18.
采用密度泛函理论确定La2与Lan F(n=1,2)分子的电子与结构特性.应用最小二乘法拟合出La2和LaF分子的Murrell-Sorbie势能函数,在此基础上推导出光谱数据和力常数.基态La2F分子具有C2v对称性的弯曲结构,电子态4A2,结合能为7.89 eV.用多体项展式理论得出La2 F的解析势能函数,其等值势能图准确再现了La2 F分子的平衡结构.  相似文献   

19.
The photo (PL) and electro (EL) luminescence in ZnS: MnLa and ZnS: La have been studied. The enhancement and quenching of emission bands have been observed on the simultaneous application of sinusoidal field and photons. The wave shape, voltage, frequency and temperature dependence of EL brightness have been reported. A study of the phosphorescence and thermoluminescence of these phosphors is also carried out and it is observed that the trap-depth changes slowly with temperature and activator concentration. An attempt has been made to calculate the trap depth by studying temperature dependence of EL brightness. The results are reported and discussed.  相似文献   

20.
The decay of naturally occurring 138La was investigated using a Ge(Li) detector system. In addition to the 33 keV X-ray, the energies of the two γ-radiations emitted were measured to be 1.436 ± 0.001 MeV and 0.788 ± 0.001 MeV. The partial half-lives of the EC branch to 138Ba and of the β-decay branch to 138Ce were calculated from intensity measurements to be (2.34 ±0.37) × 1011 and (4.7 ± 1.5) × 1011 y respectively.  相似文献   

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