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

J Jilili,U Schwingenschlögl,F Cossu

doi:10.1038/srep13762

J Jilili, U Schwingenschlögl + Show 1 more

Open Access

https://doi.org/10.1038/srep13762

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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.

Highlights

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
Nanda and coworkers[11] have studied the magnetism in LaMnO3/SrMnO3 superlattices with varying layer thicknesses, concluding that the charge reconstruction is confined to two unit cells around the interfaces
Volume changes have been observed in NaNbO3/SrTiO3 superlattices[12], for example, and it has been demonstrated that the appearance of metallicity correlates with the layer thicknesses[13]

Summary

Results

(LaMnO3)n/(SrTiO3)m superlattices are modeled by a 2 × 2 in-plane supercell of the cubic perovskite structure for taking into account possible effects of octahedral rotations. In order to assess the magnetic ground state, we study the total energies for FM and A-type AFM spin ordering for strained bulk LaMnO3 and the superlattices. A-type AFM spin ordering is 0.75 eV for strained bulk LaMnO3, whereas in the case of the superlattices it slightly decreases from 0.27 eV to 0.20 eV for increasing m and remarkably increases from 0.27 eV to 0.85 eV for increasing n, which shows that it can be attributed to the LaMnO3 layer (the Ti magnetic moments are very small). The observed small charge transfers give rise to the mentioned Ti magnetic moments but cannot explain the ferroelectric distortions in the SrTiO3 layer, which are likely direct consequences of the interface interaction

Discussion

Methods