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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.


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Projected densities of states of the Ti atoms in layers with increasing distance from the 2:8 n-IF.
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f6: Projected densities of states of the Ti atoms in layers with increasing distance from the 2:8 n-IF.

Mentions: The reduction of the minority spin band gap is explained by the projected densities of states of the Ti atoms at the n-IF in Fig. 5. The Ti 3d orbitals, being split into dxy, dyz, dxz (t2g) and , (eg) states due to the octahedral crystal field, systematically shift to lower energy for increasing n and m, which is consistent with previous experimental observations for LaAlO3/SrTiO3 interfaces34. The energetic lowering is strongest for the dxy states, which thus govern the reduction of the minority spin band gap. The orbital ordering seen in Fig. 5 decreases for increasing m, while it remains similar for increasing n. In addition, it is always more pronounced at the n-IF than at the p-IF, and almost lost at the p-IF and in the bulk-like regions of the 2:8 system. Figure 6 gives projected densities of states of Ti atoms in layers with increasing distance from the 2:8 n-IF. As to be expected, away from the n-IF the states shift to higher energy. Projected densities of states of the Mn atoms at the p-IF are shown in Fig. 7. Note that the Mn and orbitals contribute at the Fermi energy in the majority spin channel, though differently for the different systems. Since bulk LaMnO3 forced into C2h symmetry becomes metallic, the conducting Mn states are a result of the in-plane strain. The metallicity at the p-IF is substantially reduced for increasing n, especially in the 8:2 system, as the LaMnO3 layer becomes more bulk-like. Figure 8 gives projected densities of states of the Mn atoms in layers with increasing distance from the 8:2 p-IF. The distinct difference between the and states is reduced when the distance increases.


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

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

Projected densities of states of the Ti atoms in layers with increasing distance from the 2:8 n-IF.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f6: Projected densities of states of the Ti atoms in layers with increasing distance from the 2:8 n-IF.
Mentions: The reduction of the minority spin band gap is explained by the projected densities of states of the Ti atoms at the n-IF in Fig. 5. The Ti 3d orbitals, being split into dxy, dyz, dxz (t2g) and , (eg) states due to the octahedral crystal field, systematically shift to lower energy for increasing n and m, which is consistent with previous experimental observations for LaAlO3/SrTiO3 interfaces34. The energetic lowering is strongest for the dxy states, which thus govern the reduction of the minority spin band gap. The orbital ordering seen in Fig. 5 decreases for increasing m, while it remains similar for increasing n. In addition, it is always more pronounced at the n-IF than at the p-IF, and almost lost at the p-IF and in the bulk-like regions of the 2:8 system. Figure 6 gives projected densities of states of Ti atoms in layers with increasing distance from the 2:8 n-IF. As to be expected, away from the n-IF the states shift to higher energy. Projected densities of states of the Mn atoms at the p-IF are shown in Fig. 7. Note that the Mn and orbitals contribute at the Fermi energy in the majority spin channel, though differently for the different systems. Since bulk LaMnO3 forced into C2h symmetry becomes metallic, the conducting Mn states are a result of the in-plane strain. The metallicity at the p-IF is substantially reduced for increasing n, especially in the 8:2 system, as the LaMnO3 layer becomes more bulk-like. Figure 8 gives projected densities of states of the Mn atoms in layers with increasing distance from the 8:2 p-IF. The distinct difference between the and states is reduced when the distance increases.

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