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Defect-mediated ferromagnetism and controlled switching characteristics in ZnO

Published online by Cambridge University Press:  11 May 2011

Siddhartha Mal*
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695
Sudhakar Nori
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695
Jagdish Narayan
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695
John T. Prater
Affiliation:
Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

We report a detailed study of the structural, chemical, electrical, and magnetic properties of undoped ZnO thin films grown under different conditions and the films that were annealed in various environments and irradiated with an ultraviolet laser. Samples prepared in low oxygen pressure or subsequently annealed in vacuum have always been strongly magnetic. Oxygen-annealed films displayed a sequential transition from the ferromagnetic to the diamagnetic state as a function of the annealing temperature. Reversible switching of room temperature ferromagnetism and n-type conductivity have been demonstrated either by annealing in different environments or by a novel laser irradiation treatment. Enhancements in both the electrical conductivity and magnetic moment have been controlled precisely with laser pulses, without altering the crystal structure. Electron paramagnetic resonance data were found to be in good agreement with the magnetization and conductivity measurements. Our secondary ion mass spectrometer and electron energy loss spectrometer studies conclusively rule out the presence of any external ferromagnetic impurities.

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Articles
Copyright
Copyright © Materials Research Society 2011

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References

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