High temperature carrier controlled ferromagnetism in alkali doped ZnO nanorods

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Abstract
Recent efforts in developing spintronic and magneto-optoelectricmaterial for applications have relied on the use of magnetic semiconductors doped with transition metals and have met with limited success. Using a fresh synthesis approach using alkali ions we demonstrate that alkali doped zinc oxide can provide high temperature magnetic semiconductors. We report studies on nanocrystalline powder and pellets of p -type ZnO:Li and ZnO:Na that exhibit ferromagnetism up to 554 K. The ferromagnetic behavior was confirmed from magnetic hysteresis, ferromagnetic resonance, magnetic force microscopy, and explained by a model where substitutional Li + / Na + in cation site induce local magnetic moments on oxygen atoms. Optimum dopant concentrations enable ferromagnetic exchange interaction leading to high Curie temperature.