High Pressure Synthesis of New Superconductors and Related Materials

具有优异性能的新材料的发现激发了现代化学、物理和材料科学的发展。电子和磁性材料，如超导体、磁电阻、铁质材料和多铁质材料，由于相关电子系统基态的不可预测性，以及它们对化学成分和物理条件的微小变化的频繁敏感性，是一个特别的挑战。这类无机材料往往具有致密、紧密结合的结构，因此需要高压和高温来改变它们的化学结构和性质。我们建议使用高达25 GPa （250,000 bar）的压力来合成新的超导体和其他电子材料。随着稀土氧nictides RFeAsO的发现，高温超导性最近取得了突破，只有高tc铜酸盐能够超越稀土氧nictides RFeAsO。这些材料显然是超导领域的“下一件大事”，并将在未来几年主导该领域。我们已经通过制备新的超导体(TbFeAs（O，F), tbfeaso - 1-x, DyFeAs(O，F)）证明了高压方法的实用性，高压下Tc高达50 K。我们建议进一步研究新的RFeAs（O，F）和缺氧RFeAsO1-x超导体，直到稀土系列的末端，RFeAs（O，F）晶体的生长，探索其他化学取代来诱导超导性，以及RMXO和相关AM2X2材料的其他家族的研究，为发现新的超导体提供进一步的可能性。2. 具有轨道简并电子结构的钙钛矿型过渡金属氧化物具有许多突出的性能，最著名的是Cu2+氧化物的超导性和Mn3+氧化物的CMR（巨磁电阻）。许多新的或未表征的钙钛矿可以在高压下制备。我们将研究在A位和B位具有磁性三维金属的MnVO3， SrIrO3中可能的非费米液体行为，以及有趣的相LaRuO3，显然含有在氧化物中非常罕见的Ru3+态。新的过渡金属氮氧化物，如RZrO2N将被研究-这些可能会显示CMR轻掺杂，磁性和铁电顺序（多铁性）从R（稀土）矩和偏离中心的Zr位移。我们还将探索利用氧化卤化物与Li3N在压力下反应制备金属氮氧化物的一般新途径。铋过渡金属氧化物钙钛矿（如BiMnO3）是重要的多铁材料——我们将探索可能的Ruddlesden Popper模拟相Bi3M2O7和Bi2MO4，它们可能在非常高的压力（12-25 GPa）下可获得。高压形式的Bi2CuO4对超导性也很重要。作为极端条件下科学中心的一部分，最近在爱丁堡建立了一个1000吨的压力机和沃克型合成模块。我们将通过设计和制造超高压（高达25 GPa）的新样品配置来扩展方法，并在ESRF的原位实验指导下开发晶体生长方案。上述材料的结构将通过x射线和中子衍射确定，包括磁中子散射，以确定具有大偶极矩和四极矩的晚R元素的RFeAsO潜在的非常规自旋结构。电子输运和磁性将在CSEC中测量，进一步的性质将通过英国和国际合作进行探索。需要一个4年的项目来允许所有的研究都由PDRA（罗杰斯博士）和一个博士生来进行，他将专注于新的超导体。还要求提供技术和消耗品支助，使高压合成方案能够生产。

The discovery of new materials with outstanding properties motivates much of modern chemistry, physics and materials science. Electronic and magnetic materials e.g. superconductors, magnetoresistors, ferroics and multiferroics are a particular challenge due to the unpredictability of the ground states of correlated electron systems, and their frequent sensitivity to small changes in chemical composition and physical conditions. Such inorganic materials tend to have dense, strongly-bonded structures, and so high pressures and temperatures are needed to change their chemical structures and properties. We propose to use pressures up to 25 GPa (250,000 bar) to synthesise new superconductors and other electronic materials:1. A breakthrough in high temperature superconductivity has recently occurred with the discovery that doped rare earth oxypnictides RFeAsO can show critical temperatures surpassed only by the high-Tc cuprates. These materials are clearly the 'next big thing' in superconductivity and will dominate the field over the coming years. We have already demonstrated the utility of our high pressure approach by preparing new superconductors (TbFeAs(O,F), TbFeAsO1-x, DyFeAs(O,F)) with Tc's up to 50 K at high pressure. We propose an investigation of further new RFeAs(O,F) and oxygen-deficient RFeAsO1-x superconductors up to the end of the rare earth series, growth of RFeAs(O,F) crystals, exploration of other chemical substitutions to induce superconductivity, and studies of other families of RMXO and related AM2X2 materials that offer further possibilities of finding new superconductors. 2. Perovskite type transition metal oxides with orbitally-degenerate electronic configurations have many outstanding properties, most famously superconductivity in Cu2+ oxides and CMR colossal magnetoresistances) in Mn3+ oxides. Many new or uncharacterised perovskites can be made at high pressures. We will investigate MnVO3, which unusually has magnetic 3d metals at the A and B sites, possible non-Fermi liquid behaviour in SrIrO3, and the intriguing phase LaRuO3, apparently containing the Ru3+ state which is very rare in oxides.3. New transition metal oxynitrides such as RZrO2N will be investigated - these may show CMR when lightly doped, and magnetic and ferroelectric orders (multiferroism) from R (rare earth) moments and off-centre Zr displacements. We will also explore general new routes for making metal oxynitrides by reacting oxyhalides with Li3N under pressure.4. Bismuth transition metal oxide perovskites e.g. BiMnO3 are important multiferroics - we will explore possible Ruddlesden Popper analogue phases Bi3M2O7 and Bi2MO4 which may be accessible at very high pressures (12-25 GPa). The high pressure form of Bi2CuO4 will also be important for superconductivity.A 1000 tonne press and Walker type synthesis module have recently been set up in Edinburgh as part of the Centre for Science at Extreme Conditions. We will extend the methodology by designing and manufacturing a new sample configuration for very high pressures (up to 25 GPa) and developing crystal growth protocols guided by in situ experiments at ESRF.The structures of the above materials will be determined by X-ray and neutron diffraction, including magnetic neutron scattering to determine potentially unconventional spin structures of RFeAsO for late R elements with large dipolar and quadrupolar moments. Electronic transport and magnetic properties will be measured in CSEC, and further properties will be explored through UK and international collaborations.A 4 year project is needed to allow all of the research to be undertaken by a PDRA (Dr. Rodgers) and by a PhD student who will focus on the new superconductors. Technical and consumables support are also requested to enable a productive high pressure synthesis programme.