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Direct Demonstration of the Emergent Magnetism Resulting from the Multivalence Mn in a LaMnO 3 Epitaxial Thin Film System

DOI: 10.1002/aelm.201800055 DOI Help

Authors: Wei Niu (Nanjing University; Technical University of Denmark) , Wenqing Liu (Royal Holloway University of London) , Min Gu (Nanjing University) , Yongda Chen (Nanjing University) , Xiaoqian Zhang (Nanjing University) , Minhao Zhang (Nanjing University) , Yequan Chen (Nanjing University) , Ji Wang (Nanjing University) , Jun Du (Nanjing University) , Fengqi Song (Nanjing University) , Xiaoqing Pan (Nanjing University; University of California Irvine) , Nini Pryds (Technical University of Denmark) , Xuefeng Wang (Nanjing University) , Peng Wang (Nanjing University) , Yongbing Xu (Nanjing University) , Yunzhong Chen (Technical University of Denmark) , Rong Zhang (Nanjing University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Electronic Materials , VOL 11

State: Published (Approved)
Published: April 2018
Diamond Proposal Number(s): 15239

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.

Journal Keywords: dead layers; electronic reconstruction; ferromagnetism; LaMnO3; multivalence states

Subject Areas: Materials, Physics


Instruments: I06-Nanoscience