亚稳态La1-xSrxMnO3/BaTiO3全氧化物异质结磁电耦合效应研究

The all oxide artificial heterointerfaces as a fountain of novel physical properties like two-dimension electron gas, superconductivity, metal-insulator transitions and multiferroicity has flourished the field of condensed physics and materials science. We intend to carry a research on the electric and magnetic field modulated magnetic and electric transport properties in the La1-xSrxMnO3/BaTiO3 all oxide multiferroic heterostructures fabricated by facing-target magnetron sputtering method, and reveal the magnetoelectric coupling mechanism. Firstly, we achieve the metastable state by fabricating the heterostructures on the single crystal substrates with different lattice parameters. Those heterostructures can be used to study the influences of static strain effect on the magnetoelectric coupling. Secondly, by changing the doping content of Sr, an inhomogeneous distribution of carriers was introduced to the La1-xSrxMnO3 layer. We use it to study the influences of inhomogeneous state on the magnetoelectric coupling in the La1-xSrxMnO3/BaTiO3 heterostructures. Moreover, with strong correlation among charge, spin, orbital and lattice degrees at the interface, it would be possible to introduce orbital reconstruction and charge transfer by applying electric or magnetic fields to the all oxide ferromagnetic/ferroelectric heterostructures. Thus, we will be able to achieve the giant reversible modulation of their magnetic and electric transport properties and benefit the design of next generation information storage devices.

自组装全氧化物人工异质界面作为新奇物理现象如二维电子气、超导效应、金属绝缘体转变、多铁性等的源泉，成为凝聚态物理及材料科学研究领域的热点。本申请课题拟采用对向靶磁控溅射法制备全氧化物La1-xSrxMnO3/BaTiO3多铁异质结，研究电场、磁场调控下异质结的磁、电输运性质，探索磁电耦合机制。通过单晶衬底应力，获取铁磁、反铁磁共存的亚稳态异质结，研究亚稳态对异质结磁电耦合特性的影响。其次，通过改变Sr掺杂含量，促使异质结中载流子分布形成非均匀态（亚稳态），研究非均匀态对异质结磁电耦合特性的影响。由于复杂多元氧化物界面的电荷、自旋、轨道和晶格自由度存在着强关联，外加电场或磁场引起亚稳态异质结界面发生轨道重构和电荷转移，有望实现对该类型异质结磁、电输运性质的巨可逆调控，为新型磁电存储器件的设计提供依据。

自组装全氧化物人工异质界面作为新奇物理现象如二维电子气、超导效应、金属绝缘体转变、多铁性等的源泉，成为凝聚态物理及材料科学研究领域的热点。本项目基于La1-xSrxMnO3/BaTiO3多铁异质结研究了其电致电阻，发现La0.67Sr0.33MnO3的面内电阻在电场的调控下存在着易失性与非易失性。易失性状态主要是由于电场驱动下氧空位在异质结界面聚集/耗散，撤去电场后氧空位重弛豫回原始位置，表现出易失性电阻。铁电场诱导的电荷集聚/耗散导致了非易失性电阻。进一步，通过引入氧空位和空间重构，可以改变BaTiO3基底处于菱方相时La0.67Sr0.33MnO3薄膜的导电机制，实现了半导体导电到金属性导电的转变。本项目研究结果表明复杂多元氧化物界面的电荷、自旋、轨道和晶格自由度存在着强关联，外加电场诱导亚稳态异质结界面发生轨道重构和电荷转移，能实现对该类型异质结磁、电输运性质的可逆调控，为新型磁电存储器件的设计提供依据。