Intrinsic exchange bias effect in strain-engineered single antiferromagnetic LaMnO3 films
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In this work, epitaxial growth of LaMnO3 thin films on different substrates using pulsed laser deposition under tensile and compressive strain was studied. The intrinsic exchange bias effect was observed in the single A-type antiferromagnetic LaMnO3 films no matter whether the tensile or compressive strain was supplied by the substrates. Due to the lattice mismatch between the film and different substrates, the intense strain can induce MnO6 octahedral rotation in the bottom region of the film neighboring the substrate, which leads to the distortion of MnO6 octahedron and the net magnetic behavior. However, the upper part maintains the original A-type antiferromagnetic order due to strain relaxation. The exchange bias effect in single films is attributed to the coupling between the bottom canted magnetic part and the upper antiferromagnetic region. The observation of exchange bias in single films on different substrates enables the emergence of a new class of biasing components in spintronics, which are based on strain-engineering.
Keywordsmagnetic insulating state exchange bias MnO6 octahedral rotation strain and interface effects magnetic properties
本文用脉冲激光沉积系统外延生长了LaMnO3(LMO)薄膜, 研究了拉应力和压应力对薄膜磁学性质的影响, 发现在拉应力和压应力的衬底上, 外延生长这种A型反铁磁LMO薄膜, 均可出现交换偏置现象. 这是因为外应力导致衬底与薄膜界面处的MnO6氧八面体发生转动, 从而使临近衬底的LMO薄膜下层出现了净磁矩表现铁磁性; 而那些远离衬底的LMO薄膜上层则由于外应力的释放, 仍保持原有的反铁磁性. 因此, LMO薄膜中自发的交换偏置现象, 源于铁磁性与反铁磁性之间的交换耦合作用. 这种在单一LMO薄膜中实现交换偏置的现象, 为自旋阀器件的优化设计提供了一种新方法.
The authors acknowledge Beamline BL08U1A in Shanghai Synchrotron Radiation Facility (SSRF) and Beamline BL12-a in National Synchrotron Radiation Laboratory (NSRL) for X-ray absorption measurement at room temperature. This work was financially supported by the National Key R&D Program of China (2017YFB0405703), the National Natural Science Foundation of China (51871137, 61434002 and 51571136), and the Special Funds of Sanjin Scholars Program.