Defect‐induced ferromagnetic ordering in pristine cuprous oxide nanocrystals at room temperature

Herein we report the existence of room temperature ferromagnetic ordering in pristine cuprous oxide nanocrystals mediated by native point defects present in the material. To demonstrate defect‐induced magnetism, cuprous oxide nanocrystals were synthesized in a simple and sustainable route employing hydroxylamine as the reducing agent. The crystalline phase of the as‐synthesized nanocrystals was investigated and was found to have crystallized in cuprite crystal structure. The optical absorption characteristics exhibits absorption features in the visible region between 400 and 600 nm signifying the presence of optically active defects. The morphology of the sample was examined, which reveals the shape to be corner‐truncated rhombic dodecahedral and the size to be in the range of 200–250 nm. The field‐dependent magnetization measurement at room temperature indicates the presence of collective ferromagnetism with hysteresis behavior (Ms = 210 memu g−1, Mr = 43 memu g−1, Hc = 16.37 mT) due to exchange interaction between the uncompensated spin moments present on the surface of the material. We report the existence of room temperature ferromagnetic ordering in pristine cuprous oxide nanocrystals mediated by native defect states present in the material. The exchange interaction between the uncompensated spin moments derived from the vacancies present on the surface gives rise to collective ferromagnetism with hysteresis behavior.