We acknowledge financial support from Spanish MEC (MAT2003-4161 and MAT2006-13572-C02-01), FEDER program and Generalitat de Catalunya (2005SGR-00509). We would like to express our deepest gratitude to M. Varela for her assistance with the electron microscopy technique and to C. Frontera, J. Santamaria and J.L. Garcia-Muñoz for their valuable comments.
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Full Paper
Interfacial Strain: The Driving Force for Selective Orbital Occupancy in Manganite Thin Films†
Article first published online: 28 NOV 2007
DOI: 10.1002/adfm.200700137
Copyright © 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Additional Information
How to Cite
Abad, L., Laukhin, V., Valencia, S., Gaup, A., Gudat, W., Balcells, L. and Martínez, B. (2007), Interfacial Strain: The Driving Force for Selective Orbital Occupancy in Manganite Thin Films. Advanced Functional Materials, 17: 3918–3925. doi: 10.1002/adfm.200700137
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Publication History
- Issue published online: 6 DEC 2007
- Article first published online: 28 NOV 2007
- Manuscript Revised: 17 JUL 2007
- Manuscript Received: 1 FEB 2007
Funded by
- Spanish MEC. Grant Numbers: MAT2003-4161, MAT2006-13572-C02-01
- FEDER program
- Generalitat de Catalunya. Grant Number: 2005SGR-00509
- Abstract
- References
- Cited By
Keywords:
- Conductivity, metallic;
- Magnetic materials;
- Manganite;
- Perovskites;
- Structure–property relationships
Graphical Abstract
The magnetic and transport properties of homogeneously strained high quality LCMO/STO thin films are analyzed. Soft X-ray absorption spectroscopy at the O K-edge shows that interfacial strain due to substrate/film mismatch is strong enough to split the eg and t2g levels close to the film/substrate interface, promoting selective orbital occupancy with charge localization, favoring the appearance of an orbital glass insulating phase. Concomitantly, we observe an increase of the Mn4+ concentration close to this interface.
Abstract
Complex oxides with perovskite structure are the ideal arena to study a plethora of physical properties including superconductivity, ferromagnetism, ferroelectricity, piezoelectricity and more. Among them, transition metal oxides are especially relevant since they present large electronic correlations leading to a strong competition between lattice, charge, spin, and orbital degrees of freedom. In particular, manganese perovskites oxides exhibit half-metallic character and colossal magnetoresistive response rendering them as the ideal materials to develop novel concepts of oxide-electronic devices and for the study of fundamental physical interactions. Due to the close similarity between kinetic energy of charge carriers and Coulomb repulsion, tiny perturbations caused by small changes in temperature, magnetic or electric fields, strain and so forth may drastically modify the magnetic and transport properties of these materials. In particular clarifying the role of interfacial strain in manganite thin films is interesting not only for device applications but also for basic understanding of physical interactions. A better comprehension of such strongly correlated systems might lead to control the different degrees of freedom in a near future contributing to the development of the so called orbitronics, i.e. controlling and modifying at will the orbital orientation of the 3d levels in transition metals. Here we reveal the importance of interfacial strain in high quality epitaxial thin films of La2/3Ca1/3MnO3 (LCMO), grown on top of SrTiO3 (STO) and NdGaO3 (NGO) (001)-oriented substrates. We show that in such systems interfacial strain due to lattice mismatch lifts the degeneracy of the eg and t2g orbitals close to the film/substrate interface inducing Jahn-Teller like distortions and promoting selective orbital occupancy and the appearance of an orbital glass insulating state in an otherwise ferromagnetic metallic material. These results highlight the role of strain and identify it as a key parameter in orbital control.