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
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.
Transmission electron microscopy(TEM) study of SrPt2As2 reveals two incommensurate modulations appearing in the charge-density-wave(CDW) state below TCDW≈ 470 K. These two structural modulations can be well explained in terms of condensations of two-coupled phonon modes with wave vectors of q1= 0.62a*on the a*–b*plane and q2=0.23a*on the a*–c*plane. The atomic displacements occur along the b-axis direction for q1and along the c-axis direction for q2, respectively. Moreover, the correlation between q1and q2can be generally written as q1=(q2+ a*)/2 in the CDW state, suggesting the presence of essential coupling between q1and q2. A small fraction of Ir doping on the Pt site in Sr(Pt1-xIrx)2As2(x ≤ 0.06) could moderately change these CDW modulations and also affect their superconductivities.
