尖晶石铁氧体基多铁异质结的磁性与输运特性的电场调控研究

Spinel ferrites, with the characteristics of remarkable magnetic, multiferroic, transport properties, and high Curie temperatures, are wildly used in spintronics devices and multiferroic composites. As ferrimagnetic insulators, CoFe2O4 films have spin inject and resistance switching effects. The combination of spinel ferrite and ferroelectric materials can form artificial multiferroic materials. The magnetoelectric coupling and electric field modulated magnetic properties have become the hot topic. We intend to fabricate CoFe2O4 films with different oxygen vacancies intensity on ferroelectric PMN-PT substrates by using reactive cosputtering. We intend to investigate the electric field modulated magnetic, magnetoresistance and memresistance effects according to the strain effect on the lattice and the charge influenced oxygen vacancies of CoFe2O4. We will reveal the characteristics and the physical mechanisms of the strain and charge effects. The project will obtain the multi-state control of magnetic and electrical properties of spinel ferrite based multiferroic heterostructures. The results can provide the experimental and theoretical basis for the nanodevices.

尖晶石铁氧体材料具有丰富多样的电学和磁学性质以及高居里温度等优点，在自旋电子学及多铁复合结构的研究中有广泛的用途。亚铁磁绝缘体材料CoFe2O4薄膜具有自旋过滤功能和阻变效应，并且与铁电材料的结合可构成人工多铁材料，其磁电耦合特性和电控磁、电性质成为研究的热点。本申请课题拟采用反应磁控溅射技术在单晶PMN-PT铁电基片上生长具有不同氧空位密度的CoFe2O4薄膜，构成多铁异质结构。通过外加电场下PMN-PT产生的应力对CoFe2O4晶格的作用、界面电荷对CoFe2O4中氧空位的作用来调控CoFe2O4薄膜的磁性、电致电阻与磁电阻，研究其规律与物理机制，实现对尖晶石铁氧体基多铁异质结构磁、电特性的多重调控。研究结果为多铁异质结构在磁电调控纳米器件的应用提供实验和理论基础。

尖晶石铁氧体材料具有丰富多样的电学和磁学性质以及高居里温度等优点，电场调控尖晶石铁氧体材料的电输运特性与磁性，在能源和环境方面具有潜在应用价值。本工作采用磁控溅射的方法，制备了尖晶石铁氧体及其异质结构：NiFe2O4/PMN-PT异质结、CoFe2O4/La0.67Sr0.33MnO3/PMN-PT (CFO/LSMO/PMN-PT)异质结等，系统研究了电场调控下异质结的磁性与电性，研究结果表明铁电场效应与氧(空位)密切相关；电场调控下，CFO/LSMO/PMN-PT异质结的矫顽场降低~50%，有助于实现电场对磁隧道结磁电阻的调控；为了进一步研究铁电场效应对氧空位的作用机制，我们选择Co3O4, La0.67Sr0.33MnO3等氧化物半导体材料与PMN-PT结合；系统研究了外电场下半导体特性的变化，揭示了氧空位在电场调控中的作用。相关结果发表在Appl. Phys. Lett., ACS Appl. Mater. Interfaces, EPL等学术期刊上。