Direct Demonstration of the Emergent Magnetism Resulting from the Multivalence Mn in a LaMnO3 Epitaxial Thin Film System

Wei Niu, Wenqing Liu, Min Gu, Yongda Chen, Xiaoqian Zhang, Minhao Zhang, Yequan Chen, Ji Wang, Jun Du, Fengqi Song, Xiaoqing Pan, Nini Pryds, Xuefeng Wang, Peng Wang, Yongbing Xu, Yunzhong Chen*, Rong Zhang

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Atomically engineered oxide heterostructures provide a fertile ground for creating novel states, for example, a 2D electron gas at the interface between two oxide insulators, giant thermoelectric Seebeck coefficient, emergent ferromagnetism from otherwise nonmagnetic components, and colossal ionic conductivity. Extensive research efforts reveal that oxygen deficiency or lattice strain play an important role in determining these unexpected properties. Herein, by studying the abrupt presence of robust ferromagnetism (up to 1.5 µB/Mn) in LaMnO3‐based heterostructures, the multivalence states of Mn that play a decisive role in the emergence of ferromagnetism in the otherwise antiferromagnetic LaMnO3 thin films are found. Combining spatially resolved electron energy‐loss spectroscopy, X‐ray absorption spectroscopy, and X‐ray magnetic circular dichroism techniques, it is determined unambiguously that the ferromagnetism results from a conventional Mn3+‐O‐Mn4+ double‐exchange mechanism rather than an interfacial effect. In contrast, the magnetic dead layer of 5 unit cell in proximity to the interface is found to be accompanied with the accumulation of Mn2+ induced by electronic reconstruction. These findings provide a hitherto‐unexplored multivalence state of Mn on the emergent magnetism in undoped manganite epitaxial thin films, such as LaMnO3 and BiMnO3, and shed new light on all‐oxide spintronic devices.
Original languageEnglish
Article number1800055
JournalAdvanced Electronic Materials
Volume4
Issue number6
Pages (from-to)1-9
DOIs
Publication statusPublished - 2018

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