Study of electron-doped manganite single crystals using high-pressure synthesis methods

迄今为止，对Mn价态接近4+的“电子掺杂”锰氧化物的研究很少。最近，我们利用高压合成方法成功地合成了含Mn^<4+>离子的母体化合物SrMnO_3单晶。在本项目中，我们通过控制载流子数和/或晶格常数的Sr离子的部分取代，揭示了电子掺杂锰氧化物的电子和晶格状态的整体特征。特别是，我们已经发现了一种新的绝缘体-金属过渡伴随着磁过渡，这是可控的1%的载流子掺杂。此外，我们还发现了用Ba离子取代Sr离子时，Mn^<4+>离子偏离中心的铁电转变。该材料的铁电性能比传统的多铁性材料好得多。这些材料在未来的自旋电子技术中将是非常有前途的。

So far, there have been few studies on "electron-doped" manganites, the Mn valence of which is close to 4+. By using high-pressure synthesis methods, recently, we succeeded in synthesizing the single crystals of SrMnO_3, which is a parent compound with Mn^<4+> ions. In this project, by controlling the carrier number and/or lattice constant with partial substitution of Sr ions, we have revealed the overall features of electronic and lattice states for the electron-doped manganites. In particular, we have found a novel insulator-metal transition accompanied by a magnetic transition, which is controllable with 1% carrier doping. Furthermore, we have discovered a ferroelectric transition with off-center Mn^<4+> ions by substituting Sr ions with Ba ions. The ferroelectric properties are much nicer than those for the conventional multiferroic materials. These materials would be quite promising for future spintronic technology.