The characteristics of the diffuse phase transition of Pb(Fe2/3W1/3)O3 relaxor ceramics doped with different amounts of Mn are investigated. The freezing temperature Tf, obtained by fitting the ω,Tmax to the Vogel–Fulcher relationship, clearly changes with the Mn content. It increases as the Mn content increases, approaching the Tmax(1 MHz) value of the relaxor curve. A concomitant decrease in the frequency dispersion of Tmax is also observed. The freezing temperature also increases as the 1:1 order of Fe3+ and W6+on B sites increases by air annealing but decreases by oxygen annealing. It is suggested that the Mn ions, which are predominantly compensated by oxygen vacancies, form with them defect pairs and that these pairs can couple to the spontaneous polarization vectors, increasing the correlation between the dipole moments and originating the increase of the freezing temperature. It is further suggested that filling up the oxygen vacancies by oxygen annealing will decrease the defect pairs and cause the opposite effect.

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Outburst floods can have disastrous impacts on people, and are an important driving force in landscape change and have been studied widely on Earth. In China, although outburst floods have occurred frequently, they have been relatively little systematic studied. Here, we review outburst floods in China in terms of the characteristics, distribution, causes of dams and outburst floods. In terms of natural dams, landslides accounted for the majority (287 cases), followed by moraine dams (33 cases), which are mainly found on and around the Tibetan Plateau, and although other types (such as glacier and volcanic dams) were historically rare, many examples may be preserved in the geologic record. In addition, there have been thousands of outburst floods from artificial-constructed dams, the majority of which were from small earth dams. The largest reliably recorded peak discharge for an outburst flood was 1.24×10 5 m 3 /s, which occurred in Yigong, Tibet. The peak discharge of the 1975 Banqiao collapse was 7.9×10 4 m 3 /s, was the largest outburst flood of man-made dam. Our recent investigations on the Yarlung Tsangpo in Southeast Tibet have identified gravel deposits that probably record megafloods and offer great potential for paleoflood analysis.

The solubility of bismuth oxide in barium titanate was investigated by X-ray diffraction and scanning electron microscopy. Bismuth was added in two schemes: Ba 1−x Bi x TiO 3 , where only site balance was considered, and Ba 1−1.5y Bi y TiO 3 , where both site balance and charge balance were considered. The solubility limits of bismuth in BaTiO 3 sintered samples for these two schemes are slightly different, 3 and 5 at.%, respectively, at 1250°C.

The discovery of nonmagnetic Weyl semimetals (WSMs) in TaAs compounds has triggered lots of efforts in finding its magnetic counterpart. While the direct observation of the Weyl nodes and Fermi arcs in a magnetic candidate through angle-resolved photoemission spectroscopy is hindered by the complex magnetic domains. The transport features of magnetic WSMs, including negative magnetoresistivity and anomalous Hall conductivity, are not conclusive since these are sensitive to extrinsic factors like defects and disorders in lattice or magnetic ordering. Here, we systematically study the temperature dependent optical spectra of ferromagnetic Co3Sn2S2 experimentally and simulated by first-principles calculations. The many-body correlation effect due to Co 3d electrons leads to renormalization of bands by a factor about 1.33, which is moderate and the description within density functional theory is suitable. As temperature drops down, the magnetic phase transition happens and the magnetization drives the band shift through exchange splitting. The optical spectra can well detect these changes, including the transitions sensitive and insensitive to the magnetization, and those from the bands around the Weyl nodes. The results strongly support that Co3Sn2S2 is a magnetic WSM and the Weyl nodes can be tuned by magnetization with temperature change.PACS numbers: 72.15.-v, 74.70.-b, 78.30.-j Recently, the shandite compound Co 3 Sn 2 S 2 has attracted lots of attentions since it not only shows intrinsic ferromagnetism but also is proposed to have three pairs of Weyl points around the Fermi level in the first Brillouin zone (BZ) [1-3, 5]. For its quasi-two-dimensional crystal structure, low carrier density and strong anomalous Hall effect (AHE), Co 3 Sn 2 S 2 has been thought as a potential candidate to realize the quantum AHE [6,7] in its tow-dimensional (2D) limit [1,8,9]. As a candidate of magnetic Weyl semimetal (WSM) [10], the magnetic ordering states are expected to have interactions with Weyl nodes [2,3], so that the topological properties from WSM can be finely tuned through control of magnetization [2,11]. Actually, it has been found that upon cooling, the magnetization and anomalous Hall conductivity (AHC) of Co 3 Sn 2 S 2 vary accordingly [1, 2] and the first-principles calculations of AHC at different magnetization has shown their intrinsic relationship through the changes in the position of Weyl nodes [2]. To check whether this picture is true or not in realistic samples, here we have performed systematical optical spectra measurements under different temperatures (T s). The advantages of optical spectra measurements over the AHC measurements are as following: First, optical spectrum is * These authors contributed equally to this work. † hmweng@iphy.ac.cn ‡ xgqiu@iphy.ac.cn

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