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

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.