Influence of confinement regimes on magnetic property of pristine SnO2 quantum dots

Abstract

We demonstrate a clear correlation between the quantum confinement effect and magnetization of pristine tin dioxide (SnO₂) quantum dots (QDs). We have synthesized single crystalline QDs of SnO₂ above and below the exciton Bohr radius (2.7 nm). Such fine control over the size of the QDs is a challenging task. The 2 nm QDs belong to strong confinement regimes and are found to be ferromagnetic in nature, whereas 3 nm QDs are diamagnetic like bulk SnO₂. To the best of our knowledge, so far no experimental studies on the influence of confinement effect on the magnetic behaviour of SnO₂ QDs have been reported. We propose two possible mechanisms based on the theory of localization of holes due to a strong confinement effect to explain room temperature ferromagnetism in 2 nm QDs. The localization of holes is confirmed from photoluminescence and UV visible spectroscopy.