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Abstract: Single phase Mn doped 2 at % ZnO samples have been synthesized bysolid-state reaction technique. Before the final sintering at 500 C, the mixedpowders have been milled for different milling periods 6, 24, 48 and 96hours. The grain sizes of the samples are very close to each other ~ 32 \pm 4nm. However, the defective state of the samples is different from each otheras manifested from the variation of magnetic properties and electricalresistivity with milling time. All the samples have been found to beferromagnetic with clear hysteresis loops at room temperature. The maximumvalue for saturation magnetization 0.11 {\mu} B - Mn atom was achieved for 96hours milled sample. Electrical resistivity has been found to increase withincreasing milling time. The most resistive sample bears the largest saturationmagnetization. Variation of average positron lifetime with milling time bears aclose similarity with that of the saturation magnetization. This indicates thekey role played by open volume vacancy defects, presumably zinc vacancies neargrain surfaces, in inducing ferromagnetic order in Mn doped ZnO. To attainoptimum defect configuration favorable for ferromagnetism in this kind ofsamples proper choice of milling period and annealing conditions is required.

Autor: S. Chattopadhyay, S. K. Neogi, A. Sarkar, M. D. Mukadam, S. M. Yusuf, Aritra Banerjee, S. Bandyopadhyay


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