Title

Seeking large Seebeck effects in LaX(X = Mn and Co)O3/SrTiO3 superlattices by exploiting high spin-polarized effects

RIS ID

137384

Publication Details

Li, J., Wang, Y., Zhang, G., Yin, H., Chen, D., Sun, W., Shi, B. & Cheng, Z. (2019). Seeking large Seebeck effects in LaX(X = Mn and Co)O3/SrTiO3 superlattices by exploiting high spin-polarized effects. Physical Chemistry Chemical Physics, 21 (27), 14973-14983.

Abstract

SrTiO3-based transition-metal oxide heterostructures with superconducting, ferromagnetic, ferroelectric, and ferroelastic properties exhibit high application potential in the fields of energy storage, energy conversion, and spintronic devices. Meanwhile, high effective (charge)-Seebeck coefficient materials composed of a ferromagnetic layer and SrTiO3 insulator layer have been achieved but we still have blocks to pursuing high spin-Seebeck coefficient materials. Here, we use first-principles calculations combined with spin-resolved Boltzmann transport theory to investigate the spin- and effective-Seebeck coefficients in the LaX(X = Mn and Co)O3/SrTiO3 superlattice. Compared with the LaMnO3/SrTiO3 superlattice, LaCoO3/SrTiO3 with ferromagnetic ordering has high spin polarization, relatively low valence valley degeneracy but high effective mass. Utilizing these characteristics, the maximum spin-Seebeck coefficient of LaMnO3/SrTiO3 is -152 μV K-1 at 450 K along the cross-plane direction, while LaCoO3/SrTiO3 reaches -247 μV K-1 under the same conditions. Interestingly, the spin- and effective-Seebeck coefficients are amazingly consistent with each other below 200 K, which indicates that one spin channel (spin-up or spin-down) dominates the carrier transport, and the other one (spin-down or spin-up) is filtered out. These characteristics are mainly associated with the magnetic MnO2/CoO2 layers with distinct dxy and dz2 orbitals near the Fermi level. Our results clarify the relationship of spin- and effective-Seebeck coefficients and indicate that SrTiO3-based transition metal oxide heterointerfaces are a key candidate for spin caloritronics.

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Link to publisher version (DOI)

http://dx.doi.org/10.1039/c9cp02486g