Defect Driven Magnetism in Doped SnO₂ Nanoparticles: Surface Effects

Magnetism and energetics of intrinsic and extrinsic defects and defect clusters in bulk and surfaces of SnO ₂ is investigated using first-principles to understand the role of surfaces in inducing magnetism in Zn doped nanoparticles. We find that Sn vacancies induce the largest magnetic moment in bulk and on surfaces. However, they have very large formation energies in bulk as well as on surfaces. Oxygen vacancies on the other hand are much easier to create than V _Sn , but neutral and V _O ⁺² vacancies do not induce any magnetism in bulk as well as on surfaces. V _O ⁺¹ induce small magnetism in bulk and on (001) surfaces. Isolated Zn _Sn defects are found to be much easier to create than isolated Sn vacancies and induce magnetism in bulk as well on surfaces. Due to charge compensation, Zn _Sn +V _O defect cluster is found to have the lowest for-mation energy amongst all the defects; it has a large magnetic moment on (001), a small magnetic moment on (110) surface and it is non-magnetic in bulk. Thus, we find that Zn _Sn and Zn _Sn +V _O defects on the surfaces of SnO ₂ play an important role in inducing the magnetism in Zn-doped SnO ₂ nanoparticles.