Electronic structure and magnetic properties of oxygen deficient low-index surfaces of SnO2

In order to elucidate the origin of the observed ferromagnetism in SnO2 nano-particles and films, we systematically investigate the electronic structure and magnetic properties of the reduced (110), (100) and (101) surfaces of SnO2 and study the role of singly charged oxygen vacancy (V-O(1+)) at (110), (100), (101) and (001) surfaces on the electronic structure and magnetic properties of SnO2 by using first-principles calculation. The results show that the stable reduced (110), (100) and (101) surfaces of SnO2 are nonmagnetic, which is similar to early published results, where one neutral O vacancy at the low-index surfaces of SnO2 produce spin non-splitting defect states. By contrast, although at the (110), (100) and (101) surfaces of SnO2 do not induce the magnetism, V-O(1+) at the (001) surface of SnO2 induce magnetic moment, which mainly originate from partially filled 5p orbitals of the reduced Sn atom and partially filled 2p orbitals of the O atoms around the reduced Sn atom. More importantly, the magnetic coupling between moments induced by two V-O(1+) at the (001) surface of SnO2 is ferromagnetic, and this coupling can be attributed to the p-p hybridization interaction involving polarized electrons. The last result supports the experimental evidence that the observed ferromagnetism in undoped SnO2 originate from V-O(1+) at the surfaces. (C) 2016 Elsevier B.V. All rights reserved.