Defect-induced magnetism in chemically synthesized nanoscale sheets of MgO

Highly defective MgO nanosheets were prepared by a colloidal synthesis and exhibited low-temperature ferromagnetism which was significantly larger that the magnetization potentially obtainable from the low transition-metal impurity concentration. Electron paramagnetic resonance experiments confirmed that the magnetization did not significantly involve impurities and that the nanosheets consisted of strongly interacting spin clusters which disappeared upon high-temperature annealing. These spins were concentrated along extended defects, possibly as unpaired electrons trapped at oxygen vacancies.