Origins of ferromagnetism in transition-metal doped Si

Ko, V., Teo, T.L., Liew, T., Chong, T.C., MacKenzie, M., MacLaren, I. and Chapman, J.N. (2008) Origins of ferromagnetism in transition-metal doped Si. Journal of Applied Physics, 104, 033912. (doi: 10.1063/1.2963485)

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We present results of the magnetic, structural and chemical characterizations of Mn<sup>+</sup>-implanted Si displaying <i>n</i>-type semiconducting behavior and ferromagnetic ordering with Curie temperature,T<sub>C</sub> well above room temperature. The temperature-dependent magnetization measured by superconducting quantum device interference (SQUID) from 5 K to 800 K was characterized by three different critical temperatures (T*<sub>C</sub>~45 K, T<sub>C1</sub>~630-650 K and T<sub>C2</sub>~805-825 K). Their origins were investigated using dynamic secondary mass ion spectroscopy (SIMS) and transmission electron microscopy (TEM) techniques, including electron energy loss spectroscopy (EELS), Z-contrast STEM (scanning TEM) imaging and electron diffraction. We provided direct evidences of the presence of a small amount of Fe and Cr impurities which were unintentionally doped into the samples together with the Mn<sup>+</sup> ions, as well as the formation of Mn-rich precipitates embedded in a Mn-poor matrix. The observed T*<sub>C</sub> is attributed to the Mn<sub>4</sub>Si<sub>7</sub> precipitates identified by electron diffraction. Possible origins of and are also discussed. Our findings raise questions regarding the origin of the high ferromagnetism reported in many material systems without a careful chemical analysis.

Item Type:Articles
Keywords:chromium, Curie temperature, electron diffraction, electron energy loss spectra, elemental semiconductors, ferromagnetic materials, ion implantation, iron, magnetic semiconductors, magnetisation, manganese, precipitation, scanning electron microscopy, secondary ion mass spectra, semiconductor doping, silicon, SQUIDs, transmission electron microscopy
Glasgow Author(s) Enlighten ID:MacLaren, Dr Ian and MacKenzie, Dr Maureen and Chapman, Professor John
Authors: Ko, V., Teo, T.L., Liew, T., Chong, T.C., MacKenzie, M., MacLaren, I., and Chapman, J.N.
Subjects:Q Science > QC Physics
College/School:College of Science and Engineering > School of Physics and Astronomy
Research Group:Solid State Physics
Journal Name:Journal of Applied Physics
Publisher:American Institute of Physics
Copyright Holders:Copyright © 2008 American Institute of Physics
First Published:First published in Journal of Applied Physics 104:033912
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.

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