Understanding the Effects of Tensile Strain on the Structure and Magnetism of Stoichiometric LaCoO3 Films
Daniel Russell, Rebecca M. Haight, Binzhi Liu, Ali Barooni, Allen Partin, Alevtina Smekhova, Florian Kronast, L. Robert Baker, Maryam Ghazisaeidi, Jinwoo Hwang, Fengyuan Yang, Patrick M. Woodward
TL;DR
This study investigates how tensile strain affects the structure and magnetism of LaCoO3 films, revealing that strain stabilizes magnetic order.
Contribution
The novel contribution is identifying that tensile strain from SrTiO3 substrates stabilizes magnetic properties in stoichiometric LaCoO3 films.
Findings
Ferromagnetism is stabilized only in LaCoO3 films grown under tensile strain on SrTiO3 substrates.
Tensile strain leads to specific structural distortions and stabilizes high- or intermediate-spin Co3+ ions, promoting magnetic order.
Films on LaAlO3 substrates contain mostly low-spin Co3+ ions and lack magnetic order.
Abstract
Despite numerous reports of an insulating ferromagnetic state in epitaxial LaCoO3 thin films, no consensus has been reached on the details of ferromagnetism in these films. To better understand the origins of magnetic order in such films, stoichiometric LaCoO3 films have been deposited on SrTiO3(001) and LaAlO3(001) substrates using off-axis sputtering. This technique allows growth to occur in conditions that minimize deviations from the ideal stoichiometry. SQUID magnetometry shows that ferromagnetism is stabilized only in films grown under tensile strain on SrTiO3. The magnetic properties of these films (T C ≈ 70 K, M sat ≈ 0.3 μB/Co, and H C ≈ 5 kOe) are essentially independent of thickness, consistent with nearly uniform magnetization. At room temperature, strain induced by the SrTiO3 substrate breaks the rhombohedral symmetry of the bulk structure, leading to a – a – c 0 octahedral…
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Taxonomy
TopicsMagnetic and transport properties of perovskites and related materials · Electronic and Structural Properties of Oxides · Advanced Condensed Matter Physics