Magnetic tunnel junction (MTJ) is one of the cornerstones of modern information technologies. Bringing MTJ's operation beyond the conventional binary regime, enabled by tunneling magnetoresistance (TMR) effect, is highly promising for prospective memory technologies and neuromorphic hardware development. In this paper, we demonstrate multilevel magnetoresistance states in an all-perovskite-oxide La0.7Sr0.3MnO3 (LSMO)/BaTiO3/LSMO heterostructure grown on MgO substrates. Unlike traditional TMR, we observe four distinct regions of increased magnetoresistance, which result in three magnetic field-induced resistance states in total. We show that the observed phenomenon arises from the low-field magnetoresistance effect, which occurs in the two epitaxial LSMO layers, independently and at different values of the magnetic field. The effect is well simulated by a model based on the presence of structural defects and non-uniform deformations in the LSMO layers, induced by the large lattice mismatch of the LSMO with the MgO substrate. We believe that our findings contribute to the understanding of complex magnetoresistance effects in MTJs and can be taken into consideration for the design of multi-bit memory cells or neuromorphic devices.

中文翻译：

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MgO 上生长的 La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 异质结构的多级磁阻态


磁隧道结（MTJ）是现代信息技术的基石之一。通过隧道磁阻 (TMR) 效应，使 MTJ 的操作超越传统的二元状态，对于未来存储技术和神经形态硬件的开发来说是非常有前景的。在本文中，我们展示了在 MgO 基底上生长的全钙钛矿氧化物 La0.7Sr0.3MnO3 (LSMO)/BaTiO3/LSMO 异质结构中的多级磁阻态。与传统的 TMR 不同，我们观察到四个不同的磁阻增加区域，总共导致三种磁场感应电阻状态。我们表明，所观察到的现象是由低场磁阻效应引起的，该效应独立地在不同的磁场值下发生在两个外延 LSMO 层中。该效应可以通过基于 LSMO 层中存在的结构缺陷和不均匀变形的模型很好地模拟，这些缺陷和变形是由 LSMO 与 MgO 基底的大晶格失配引起的。我们相信，我们的发现有助于理解 MTJ 中复杂的磁阻效应，并且可以在多位存储单元或神经形态设备的设计中得到考虑。