Condensed Matter Science and Technology Institute, School of Science, Harbin Institute of Technology, Harbin, 150081, China.
School of Physical and Mathematical Sciences & School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore.
Nat Commun. 2018 May 15;9(1):1897. doi: 10.1038/s41467-018-04233-5.
Complex-oxide materials exhibit physical properties that involve the interplay of charge and spin degrees of freedom. However, an ambipolar oxide that is able to exhibit both electron-doped and hole-doped ferromagnetism in the same material has proved elusive. Here we report ambipolar ferromagnetism in LaMnO, with electron-hole asymmetry of the ferromagnetic order. Starting from an undoped atomically thin LaMnO film, we electrostatically dope the material with electrons or holes according to the polarity of a voltage applied across an ionic liquid gate. Magnetotransport characterization reveals that an increase of either electron-doping or hole-doping induced ferromagnetic order in this antiferromagnetic compound, and leads to an insulator-to-metal transition with colossal magnetoresistance showing electron-hole asymmetry. These findings are supported by density functional theory calculations, showing that strengthening of the inter-plane ferromagnetic exchange interaction is the origin of the ambipolar ferromagnetism. The result raises the prospect of exploiting ambipolar magnetic functionality in strongly correlated electron systems.
复合氧化物材料表现出涉及电荷和自旋自由度相互作用的物理性质。然而，一种能够在同一种材料中同时表现出电子掺杂和空穴掺杂铁磁性的双极性氧化物一直难以实现。在这里，我们报告了 LaMnO 中的双极性铁磁性，其铁磁有序具有电子-空穴不对称性。从未掺杂的原子级薄 LaMnO 薄膜开始，我们根据施加在离子液体栅极上的电压的极性，通过静电方式对材料进行电子或空穴掺杂。磁输运特性表明，在这种反铁磁化合物中，无论是电子掺杂还是空穴掺杂都会诱导铁磁有序，并导致具有巨大磁电阻的绝缘体-金属转变，表现出电子-空穴不对称性。这些发现得到了密度泛函理论计算的支持，表明增强层间铁磁共振相互作用是双极性铁磁性的起源。这一结果提出了在强关联电子系统中利用双极性磁性功能的前景。
