Tuning the magnetic properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">La</mml:mi><mml:mi mathvariant="normal">Co</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>thin films by epitaxial strain

Fuchs, D.; Arac, Erhan; Pinta, C.; Schuppler, S.; Schneider, R.; Löhneysen, H. v.

doi:10.1103/physrevb.77.014434

Cited by 229 publications

(231 citation statements)

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“…Another thin film study by Fuchs et al connected structural distortions to the presence of ferromagnetic order, estimating that the Co-O-Co angle above which there can be ferromagnetism is approximately 160 • . [16,40] All of our data show Co-O-Co angles well above this value, with the minimum angle seen at 162.8 • .…”

Section: Discussionmentioning

confidence: 70%

“…Thin film studies [16,18,40] have suggested that LCO thin films grown on certain substrates exhibit ferromagnetic long-range order, in particular when the substrate induces tensile stress at the interface with LCO. Sterbinsky et al reported that a 20 nm film of LCO deposited on a SrTiO 3 (STO) substrate had a significantly elongated in-plane Co-O bond length and a shortened out-of-plane bond length compared to the bulk value.…”

Section: Discussionmentioning

confidence: 99%

“…Seo et al argued that strained LCO heterostructures can induce thermal spin state transitions [15]. By depositing LCO thin films onto different substrates, Fuchs et al successfully tuned the ferromagnetic ordering of LCO; [16] an increase in epitaxial strain between the substrate and film was observed to correlate with an increase in the effective magnetic moment µ B /Co. A previous study suggested that ferromagnetic effects are induced by strain from Co-impurities in bulk powders of LCO [17] and that the Co-O-Co bond angle, γ, is a structural indicator of the strength of ferromagnetic ordering.…”

Section: Introductionmentioning

confidence: 99%

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The effects of Co₃O₄on the structure and unusual magnetism of LaCoO₃

Durand

Hamil

Belanger

et al. 2015

J. Phys.: Condens. Matter

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Bulk LawCoO3 particles with w = 1.1, 1.0, 0.9, 0.8, and 0.7 were synthesized using starting materials with varying molar ratios of La2O3 and Co3O4. The resulting particles are characterized as LaCoO3 crystals interfaced with a crystalline Co3O4 phase. X-ray and neutron scattering data show little effect on the average structure and lattice parameters of the LaCoO3 phase resulting from the Co3O4 content, but magnetization data indicate that the amount of Co3O4 strongly affects the ferromagnetic ordering at the interfaces below TC ≈ 89 K. In addition to ferromagnetic long-range order, LaCoO3 exhibits antiferromagnetic behavior with an unusual temperature dependence. The magnetization for fields 20 Oe ≤ H ≤ 5 kOe is fit to a combination of a power law ((T − TC )/TC ) β behavior representing the ferromagnetic long-range order and sigmoid-convoluted Curie-Weiss-like behavior representing the antiferromagnetic behavior. The critical exponent β = 0.63 ± 0.02 is consistent with 2D (surface) ordering. Increased Co3O4 correlates well to increased ferromagnetism. The weakening of the antiferromagnetism below T ≈ 40 K is a consequence of the lattice reaching a critical rhombahedral distortion as T is decreased for core regions far from the Co3O4 interfaces. We introduce a model that describes the ferromagnetic behavior of the interface regions and the unusual antiferromagnetism of the core regions.

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Section: Discussionmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The effects of Co₃O₄on the structure and unusual magnetism of LaCoO₃

Durand

Hamil

Belanger

et al. 2015

J. Phys.: Condens. Matter

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“…Furthermore, strain engineering in these oxide heterostructures opens up routes for creating novel electronic phases [2][3][4]. An exciting example is the recent demonstration of biaxial tensile strain stabilizing an insulating ferromagnetic (FM) ground state in LaCoO 3 (LCO) [5][6][7][8][9][10][11][12][13][14]. Though LCO is a classic example of a correlated 3d transition metal perovskite oxide [15,16], FM correlation has never been observed for the bulk ground state where the Co 3+ ions exist in the so-called low spin (LS) state (total spin per Co S=0) [15].…”

Section: Introductionmentioning

confidence: 99%

Strain-driven spin-state transition and superexchange interaction in LaCoO3:Abinitiostudy

2012

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Using spin density functional theory with the Hubbard correction we investigate the magnetic structure of strained LaCoO 3 . We show that beyond biaxial tensile strain of 2.5%, local magnetic moments originating from the high spin (HS) state of Co 3+ emerge in a low spin (LS) Co 3+ matrix. In contrast, we find that compressive strain is not able to stabilize a magnetic state due to geometric constraints. LaCoO 3 accommodates tensile strain via spin state disproportionation resulting in an unusual sublattice structure. In tensile-strained LaCoO 3 , the first nearest neighbor (n.n.) exchange coupling is ferromagnetic (FM) while the second n.n. interaction is stronger and antiferromagnetic (AFM). This unusual feature of the exchange parameters is qualitatively verified with a model superexchange calculation. Due to the competition between the FM and AFM couplings in the system, we find that the most probable magnetic structure of tensile-strained LCO is a canted-spin structure, which may explain the relatively small observed magnetic moment of 0.7μ B /Co 3+ .

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“…The possibility to control magnetism in thin films and multilayers of perovskite oxides by epitaxial strain, [1][2][3] oxygen stoichiometry, 4-7 chemical substitution, 8,9 and substrate crystalline symmetry 10,11 has rendered such materials important model systems for fundamental studies of magnetic structure as well as attractive candidates for device applications. Advances in fabrication of complex oxide thin film nanostructures 12 and the recent development of novel tools for magnetic imaging with high spatial resolution have made the study of such systems on the nanometer length scale a realistic endeavor.…”

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confidence: 99%