铁磁-反铁磁相共存驱动的超薄La0.67Sr0.33MnO3薄膜中的新兴交换偏置
Emergent exchange bias in ultra-thin La0.67Sr0.33MnO3 films driven by ferro-antiferromagnetic phase coexistence
AI总结：
研究超薄La0.67Sr0.33MnO3薄膜，虽无工程化FM-AFM界面却产生与厚度无关的EB。通过角磁光克尔效应测量、X射线光电子能谱及简单界面交换模型，发现氧缺乏驱动内部FM-AFM界面，为单相锰氧化物薄膜交换偏置提供新途径。
AI中文摘要：
超薄La0.67Sr0.33MnO3（LSMO）薄膜通常被视为单相铁磁体，但其维度降低增强了氧化学计量和局部结构畸变的影响。本文表明，厚度在3至17纳米之间的LSMO层尽管没有工程化的铁磁-反铁磁（FM-AFM）界面，却能产生强大且与厚度无关的交换偏置（EB）。角磁光克尔效应测量揭示了可重现的磁滞回线偏移，180度旋转时符号反转，证实其内在起源。X射线光电子能谱显示Mn2+分数与厚度无关（约20%），表明在Mn3+/Mn4+铁磁基质中存在缺氧还原区域。一个简单的界面交换模型表明，仅需亚百分比分数的反铁磁（或受挫自旋冰状）区域就能产生观测到的EB。这些结果表明，超薄LSMO可自发形成由氧缺乏驱动的内部FM-AFM界面，揭示了在名义上单相锰氧化物薄膜中产生交换偏置的新途径。
英文摘要：
Ultra-thin La0.67Sr0.33MnO3 (LSMO) films are generally regarded as single-phase ferromagnets, yet their reduced dimensionality enhances the impact of oxygen stoichiometry and local structural distortions. Here we demonstrate that LSMO layers with thicknesses between 3 and 17 nm develop a robust and thickness-independent exchange bias (EB) despite the absence of an engineered ferromagnetic-antiferromagnetic (FM-AFM) interface. Angular magneto-optical Kerr effect measurements reveal a reproducible hysteresis-loop shift that reverses sign upon 180-degree rotation, confirming its intrinsic origin. X-ray photoelectron spectroscopy shows a thickness-independent Mn2+ fraction (about 20 percent), indicating the presence of oxygen-deficient reduced regions embedded within the Mn3+/Mn4+ ferromagnetic matrix. A simple interfacial-exchange model suggests that only a sub-percent fraction of antiferromagnetic (or frustrated spin-ice-like) regions is required to generate the observed EB. These results demonstrate that ultra-thin LSMO can spontaneously host internal FM-AFM interfaces driven by oxygen deficiency, revealing an emergent route to exchange bias in nominally single-phase manganite films.
