Insulating ferromagnetic oxide films: the controlling role of oxygen vacancy ordering

Journal Article · Wed Jan 01 00:00:00 EST 2014 · Physical Review Letters

OSTI ID:1128995

Salafranca Laforga, Juan I ^[1]; Salafranca, Juan ^[2]; Biskup, Nevenko ^[1]; Mehta, Virat ^[3]; Oxley, Mark P ^[1]; Suzuki, Yuri ^[4]; Pennycook, Stephen J ^[5]; Pantelides, Sokrates T. ^[6]; Varela del Arco, Maria ^[1]

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1. ORNL
2. Universidad Complutense de Madrid, Spain
3. University of California, Berkeley
4. Stanford University
5. University of Tennessee, Knoxville (UTK)
6. Vanderbilt University, Nashville

The origin of ferromagnetism in strained epitaxial LaCoO3 films has been a long-standing mystery. Here, we combine atomically resolved Z-contrast imaging, electron-energy-loss spectroscopy, and density-functional calculations to demonstrate that, in epitaxial LaCoO3 films, oxygen-vacancy superstructures release strain, control the film s electronic properties, and produce the observed ferromagnetism via the excess electrons in the Co d states. Although oxygen vacancies typically dope a material n-type, we find that ordered vacancies induce Peierls-like minigaps which, combined with strain relaxation, trigger a nonlinear rupture of the energy bands, resulting in insulating behavior.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1128995
• Journal Information: Physical Review Letters, Vol. 112
• Country of Publication: United States
• Language: English