Unexpected magnetic properties in carbon-doped SnO2 from first-principles calculation

We employ spin-polarized density functional theory (DFT) calculations within generalized gradient approximation (GGA) to study the electronic structure and magnetic properties of C-doped SnO2 (SnO2:C) bulk and thin films. Our results indicate that a singly substitutional C (C-O) does not induce magnetism, while the C-O-C-O pairs can unexpectedly activates short-range ferromagnetism in SnO2 bulk. The intrinsic defect O vacancy (V-O) triggers local moment on the isolated C-O atom but do not enhance the ferromagnetic (FM) coupling between C-O atoms. When the substitutional C-O atoms located at the surface of SnO2 thin films, system exhibits anti-ferromagnetic (AFM) feature, which is inconsistent with experimental observation. This diversity of magnetic behavior in SnO2:C system highlights the delicate interplay between electron correlations and localization. The magnetic properties are closely related to the intrinsic defect V-O and the reduction of some Sn+4 ions to Sn+2 as a possible charge compensation mechanism. Crown Copyright (C) 2013 Published by Elsevier B. V. All rights reserved.