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MA: Magnetismus

MA 24: Magnetic Thin Films III

MA 24.10: Vortrag

Donnerstag, 30. März 2006, 12:30–12:45, HSZ 03

Magnetic and Charge Ordering at Digital Perovskite Interfaces — •Rossitza Pentcheva¹ and Warren E. Pickett² — ¹Section Crystallography, Dept. of Earth and Environmental Sciences, University of Munich — ²Department of Physics, University of California, Davis, U.S.A.

Local charge mismatch can lead to unexpected phenomena even at the interfaces (IFs) of well understood ‘simple’ insulators: For example Ohtomo and Hwang [1] measured a metallic high mobility character at the n-type interface between the band-insulators LaAlO₃ and SrTiO₃, while the p-type interface was found to be insulating. To explain these experimental findings, we performed density-functional theory calculations employing the FP-LAPW-method within the WIEN2k implementation including a Hubbard-type on site Coulomb repulsion (DFT+U). Although both bulk materials are nonmagnetic, at the n-type interface, a charge and orbitally ordered (CO/OO) state is realized in the TiO₂-layer with ferromagnetically coupled Ti³⁺-ions and nonmagnetic Ti⁴⁺-ions arranged in a checkerboard manner. We show that at an ideal defect-free p-type IF only strong correlations in the oxygen 2p-bands can account for the measured insulating behavior: A disproportionated, CO/OO magnetic oxygen hole is formed in the AlO₂-layer. Other mechanisms for charge accommodation such as ordered defects are also investigated.

[1] A. Ohtomo and H.Y. Hwang, Nature 423, 378 (2002).