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Trends in (LaMnO3)n/(SrTiO3)m superlattices with varying layer thicknesses.

Jilili J, Cossu F, Schwingenschlögl U - Sci Rep (2015)

Bottom Line: The electronic structure turns out to be highly sensitive to the onsite Coulomb interaction.In contrast to bulk SrTiO3, strongly distorted O octahedra are observed in the SrTiO3 layers with a systematic off centering of the Ti atoms.The systems favour ferromagnetic spin ordering rather than the antiferromagnetic spin ordering of bulk LaMnO3 and all show half-metallicity, while a systematic reduction of the minority spin band gaps as a function of the LaMnO3 and SrTiO3 layer thicknesses originates from modifications of the Ti dxy states.

View Article: PubMed Central - PubMed

Affiliation: KAUST, PSE Division, Thuwal 23955-6900, Kingdom of Saudi Arabia.

ABSTRACT
We investigate the thickness dependence of the structural, electronic, and magnetic properties of (LaMnO3)n/(SrTiO3)m (n, m = 2, 4, 6, 8) superlattices using density functional theory. The electronic structure turns out to be highly sensitive to the onsite Coulomb interaction. In contrast to bulk SrTiO3, strongly distorted O octahedra are observed in the SrTiO3 layers with a systematic off centering of the Ti atoms. The systems favour ferromagnetic spin ordering rather than the antiferromagnetic spin ordering of bulk LaMnO3 and all show half-metallicity, while a systematic reduction of the minority spin band gaps as a function of the LaMnO3 and SrTiO3 layer thicknesses originates from modifications of the Ti dxy states.

No MeSH data available.


Related in: MedlinePlus

Left: Structure of the (LaMnO3)n/(SrTiO3)m superlattice for n:m = 2:4. Right: Schematic view of the Mn-O and Ti-O bonds perpendicular to the interfaces.
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f2: Left: Structure of the (LaMnO3)n/(SrTiO3)m superlattice for n:m = 2:4. Right: Schematic view of the Mn-O and Ti-O bonds perpendicular to the interfaces.

Mentions: Structural optimization of the superlattices with and without onsite interaction is found to yield substantial differences in the electronic structure, especially near the Fermi level. More specifically, the minority channel shows a metallic character without onsite interaction for n:m = 2:2 (2 unit cells of LaMnO3 alternate with 2 unit cells of SrTiO3), whereas with onsite interaction we obtain a half-metallic character. The supercells have C2h point group symmetry (tetragonal perovskite structure). An optimized in-plane lattice constant of 5.56 Å is obtained for the 2:2 system and is used for the larger superlattices. The out-of-plane lattice constant is optimized individually in each case. Starting from the 2:2 system, we fix the LaMnO3 thickness and increase the SrTiO3 thickness (2:4, 2:6, 2:8) or fix the SrTiO3 thickness and increase the LaMnO3 thickness (4:2, 6:2, 8:2). The 4:4 system is also considered for comparison. Figure 2(left) illustrates the 2:4 system as an example. There are two types of interfaces, the n-type LaO/TiO2 interface and the p-type SrO/MnO2 interface, denoted in the following as n-IF and p-IF, respectively. The nomenclature refers to the compensating charges formed at the and contacts, respectively.


Trends in (LaMnO3)n/(SrTiO3)m superlattices with varying layer thicknesses.

Jilili J, Cossu F, Schwingenschlögl U - Sci Rep (2015)

Left: Structure of the (LaMnO3)n/(SrTiO3)m superlattice for n:m = 2:4. Right: Schematic view of the Mn-O and Ti-O bonds perpendicular to the interfaces.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4555181&req=5

f2: Left: Structure of the (LaMnO3)n/(SrTiO3)m superlattice for n:m = 2:4. Right: Schematic view of the Mn-O and Ti-O bonds perpendicular to the interfaces.
Mentions: Structural optimization of the superlattices with and without onsite interaction is found to yield substantial differences in the electronic structure, especially near the Fermi level. More specifically, the minority channel shows a metallic character without onsite interaction for n:m = 2:2 (2 unit cells of LaMnO3 alternate with 2 unit cells of SrTiO3), whereas with onsite interaction we obtain a half-metallic character. The supercells have C2h point group symmetry (tetragonal perovskite structure). An optimized in-plane lattice constant of 5.56 Å is obtained for the 2:2 system and is used for the larger superlattices. The out-of-plane lattice constant is optimized individually in each case. Starting from the 2:2 system, we fix the LaMnO3 thickness and increase the SrTiO3 thickness (2:4, 2:6, 2:8) or fix the SrTiO3 thickness and increase the LaMnO3 thickness (4:2, 6:2, 8:2). The 4:4 system is also considered for comparison. Figure 2(left) illustrates the 2:4 system as an example. There are two types of interfaces, the n-type LaO/TiO2 interface and the p-type SrO/MnO2 interface, denoted in the following as n-IF and p-IF, respectively. The nomenclature refers to the compensating charges formed at the and contacts, respectively.

Bottom Line: The electronic structure turns out to be highly sensitive to the onsite Coulomb interaction.In contrast to bulk SrTiO3, strongly distorted O octahedra are observed in the SrTiO3 layers with a systematic off centering of the Ti atoms.The systems favour ferromagnetic spin ordering rather than the antiferromagnetic spin ordering of bulk LaMnO3 and all show half-metallicity, while a systematic reduction of the minority spin band gaps as a function of the LaMnO3 and SrTiO3 layer thicknesses originates from modifications of the Ti dxy states.

View Article: PubMed Central - PubMed

Affiliation: KAUST, PSE Division, Thuwal 23955-6900, Kingdom of Saudi Arabia.

ABSTRACT
We investigate the thickness dependence of the structural, electronic, and magnetic properties of (LaMnO3)n/(SrTiO3)m (n, m = 2, 4, 6, 8) superlattices using density functional theory. The electronic structure turns out to be highly sensitive to the onsite Coulomb interaction. In contrast to bulk SrTiO3, strongly distorted O octahedra are observed in the SrTiO3 layers with a systematic off centering of the Ti atoms. The systems favour ferromagnetic spin ordering rather than the antiferromagnetic spin ordering of bulk LaMnO3 and all show half-metallicity, while a systematic reduction of the minority spin band gaps as a function of the LaMnO3 and SrTiO3 layer thicknesses originates from modifications of the Ti dxy states.

No MeSH data available.


Related in: MedlinePlus