Light-Induced Spontaneous Magnetization in Doped Colloidal Quantum Dots

Abstract

Saturated Magnetism in Photoexcited Nanocrystals Switching the magnetic state of semiconductors with either an electric field or by light absorption is a key requirement for spintronics, in which devices are based on electronic spin state rather than charge. In semiconductor nanoparticles doped with magnetic ions, excitons can form a spin state, a magnetic polaron, but often the effect is limited to low temperatures (below 30 kelvin) and does not saturate in the absence of an applied magnetic field. Beaulac et al. (p. 973 ) report the synthesis of Mn-doped CdSe nanocrystals in which the quantum confinement effects lead to long exciton lifetimes. Photoexcitation results in exchange fields that can exceed 30 Tesla at low temperatures and that persist even up to room temperature in the absence of an applied magnetic field.