单相磁电多铁性体研究进展

文章从电磁耦合现象及磁电效应出发,简要介绍了单相磁电多铁性体(铁电磁体)的最新研究进展。     

Ferroelectric behaviour of 30nm BaTiO3 ceramics prepared by high pressure assisted sintering

Dense nanocrystalline BaTiO3 ceramics with a homogeneous grain size of 30 nm was obtained by pressure assisted sintering. The ferroelectric behaviour of the ceramics was characterized by the dielectric peak at around 120 ℃, the P-E hysteresis loop and some ferroelectric domains. These experimental results indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm. The ferroelectric property decreasing with decreasing grain size can be explained by the lowered tetragonality and the ＇dilution＇ effect of grain boundaries.     

第二类拓扑外尔半金属WP2高压超导相的常压截获

第二类拓扑外尔半金属WP₂高压下发生超导转变,然而,高压超导相能否在常压截获还没有相关报道.本文对密封于金刚石对顶砧中的WP₂高压超导相在室温条件下快速卸压至不同压强,原位测量电阻-温度曲线,验证能否在常压截获高压超导相.研究表明：WP₂的高压超导相可以在常压截获,从而提供了一个通过角分辨光电子能谱和扫描隧道谱探寻马约拉纳零能模的拓扑超导体材料平台.     

Study of superstructure II in multiferroic BiMnO3

The crystal structure of the minor phase, named superstructure II, existing in multiferroic compound BiMnO3 has been studied by electron diffraction and high-resolution transmission electron microscopy. Domains of major and minor phases coexisting in BiMnO3 were observed in high-resolution electron microscope images. The unit cell of minor phase was determined to be triclinic with the size 4×4×4 times as large as the distorted perovskite subcell. The [111] and [101] projected structure maps of the minor phase have been derived from the corresponding images by means of the image processing. A possible rough three-dimensional （3D） structure model was proposed based on the 3D structural information extracted from the two projected structure maps. Since there is no inversion centre in the proposed model, the minor phase may contribute to the ferroelectric property of BiMnO3.     

Mn_(3)Sn的高压物性研究

非共线三角晶格的反铁磁体Mn_(3)Sn,由于其动量空间中非零的贝里曲率而表现出反常霍尔效应.利用金刚石对顶砧研究压力对Mn_(3)Sn低温电输运性质和反常霍尔效应的影响.结果表明:Mn_(3)Sn在0~60GPa压力范围内保持金属导电行为;从非共线磁有序到螺旋磁有序的转变温度随压力增加先降低,在5.5GPa以上迅速升高,对应一个等结构电子拓扑转变;Mn_(3)Sn的反常霍尔效应在5.5GPa被完全抑制.     

单相磁电多铁性体研究进展

文章从电磁耦合现象及磁电效应出发,简要介绍了单相磁电多铁性体(铁电磁体)的最新研究进展。     

Dielectric Properties of Fine-Grained BaTiO3 Ceramics under High Pressure

We investigate the temperature dependence of the dielectric constant of BaTiO3 ceramic with coarse to nanograin size under different hydrostatic high pressures up to 5000 bar in the range between room temperature and 200℃. The ferroelectric-to-paraelectric phase transition temperatures Tc are determined from the peak of dielectric constant versus temperature. The values of average grain-size are estimated from the SEM images. It is found that the magnitude of dTc/dp varies considerably from sample to sample depending on grain size. The Curie point Tc of the sample with small grain size decreases more sharply than that of samples with larger one.     

二维层状材料FePSe3的高压物性

FePSe₃在高压下会出现半导体到金属的转变、超导电性以及高自旋到低自旋的转变等多种有趣的物理现象，但目前对其在高压下的晶体结构分析仍以理论研究为主，结构的不确定阻碍了对其物理性质的深入研究。为此，利用金刚石对顶砧结合高压拉曼光谱、高压同步辐射X射线衍射以及高压电输运测量，对FePSe₃在高压下的行为进行了研究。结果表明，FePSe₃在低于60.0 GPa的压力范围内经历了3次结构相变，完成了LP—HP1—HP2—HP3的转变。首次在实验上观测到FePSe₃的高压新相HP2和HP3，并给出其可能的空间对称群。HP2相和HP3相具有超导电性，超导温度随压力的升高而降低，致使超导相图呈现“穹顶”状。研究结果为进一步厘清FePSe₃的压致相变行为提供了重要的实验支撑。     

三重兼并费米子拓扑半金属MoP高压超导相的低压截获

碳化钨结构的三重兼并费米子拓扑半金属MoP高压下发生超导转变，然而，高压超导相能否在低压甚至常压截获尚不清楚.本文对两个密封于金刚石对顶砧中的MoP高压超导相在室温条件下进行快速卸压，通过测量低温电阻对温度的依赖关系，验证能否在低压甚至常压截获高压超导相.实验结果表明：初始压力61.5 GPa的样品#1,超导电性可截获的最低压力为44.2 GPa;初始压力95.0 GPa的样品#2,超导电性可截获的最低压力为3.5 GPa.