High-quality single crystals of A-site ordered perovskite oxides CaCu3Ru4O12 were synthesized by flux method with Cu O serving as a flux. The typical size of these single crystals was around 1 × 1 × 1 mm3 and the lattice constant was determined to be 7.430 ± 0.0009 ?A by using x-ray single crystal diffraction. The surfaces of the samples were identified to be(100) surface. The high quality of the single crystal samples was confirmed by the rocking curve data which have a full width at half maximum of approximately 0.02 degree. The x-ray photoelectron spectroscopy measurement was performed and the temperature-dependent specific heat, magnetic susceptibility, and electric resistivity were measured along the [100]direction of the single crystals. All these measurements showed that the physical properties of Ca Cu3Ru4O12 single crystals are similar to that of polycrystals. However, the single crystals have a lower Curie susceptibility tail and a smaller residual resistivity than polycrystals, which indicates that the amount of paramagnetic impurities can be controlled by tuning the number of defects in CaCu3Ru4O12 samples.
The vortex domains, structural properties and ferroelectric polarization in Y1-xInxMn O3 with 0 B x B 0.6have been extensively investigated in well-characterized samples. X-ray diffraction measurements demonstrated that the lattice parameters change continuously following the substitution of In for Y. Measurements of magnetic susceptibilities revealed that In substitution could visibly affect the magnetic transition and low-temperature magnetic properties. Transmission electron microscopy study showed that In substitution could result in notable decrease of the size of ferroelectric vortex domains. Cs-corrected scanning transmission electron microscopy observations and our careful analysis on atomic-poling configurations demonstrate that the ferroelectric polarizations of Y1-xInxMn O3 are suppressed with the increase of In content.
Li WangFu-Kuo ChiangJun LiChao MaHuai-Xin YangJian-Qi Li
Iron-chalcogenide compounds with FeSe(Te, S) layers did not attract much attention until the discovery of high-T c superconductivity (SC) in the iron-pnictide compounds at the begining of 2008. Compared with FeAs-based superconductors, iron-chalcogenide superconductors have aroused enormous enthusiasm to study the relationship between SC and magnetisms with several distinct features, such as different antiferromagnetic ground states with relatively large moments in the parents, indicating possibly different superconducting mechanisms, the existence of the excess Fe atoms or Fe vacancies in the crystal lattice. Another reason is that the large single crystals are easily grown for the iron-chalcogenide compounds. This review will focus on our exploration for the iron-chalcogenide superconductors and discussion on several issues, including the crystal structure, magnetic properties, superconductivity, and phase separation. Some of them reach a consensus but some important questions still remain to be answered.
Crystal structures and microstructural features, such as structural phase transitions, defect structures, and chemical and structural inhomogeneities, are known to have profound effects on the physical properties of superconducting materials. Recently, many studies on the structural properties of Fe-based high-T c superconductors have been published. This review article will mainly focus on the typical microstructural features in samples that have been well characterized by physical measurements. (i) Certain common structural features are discussed, in particular, the crystal structural features for different superconducting families, the local structural distortions in the Fe2Pn2 (Pn = P, As, Sb) or Fe2Ch2 (Ch = S, Se, Te) blocks, and the structural transformations in the 122 system. (ii) In FeTe(Se) (11 family), the superconductivity, chemical and structural inhomogeneities are investigated and discussed in correlation with superconductivity. (iii) In the K0.8Fe1.6+x Se2system, we focus on the typical compounds with emphasis on the Fe-vacancy order and phase separations. The microstructural features in other superconducting materials are also briefly discussed.
The measurements on temperature dependences of magnetic susceptibility χ(T), specific heat C(T), and electrical resistivity ρ(T) were carried out for the antiferromagnetic(AFM)(Ce_(1-x)La_x)_2Ir_3Ge_5(0 ≤ x ≤ 0.66) system. It was found that the Neel temperature TNdecreases with increasing La content x, and reaches 0 K near a critical content xcr =0.6. A new phase diagram was constructed based on these measurements. A non-Fermi liquid behavior in ρ(T) and a log T relationship in C(T) were found in the samples near xcr, indicating them to be near an AFM quantum critical point(QCP) with strong spin fluctuation. Our finding indicates that(Ce_(1-x)La_x)_2Ir_3Ge_5 may be a new platform to search for unconventional superconductivity.
