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Science 25 January 2002:
Vol. 295. no. 5555, pp. 651 - 654
DOI: 10.1126/science.1066348
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Reports

A Group-IV Ferromagnetic Semiconductor: MnxGe1-x

Y. D. Park,* A. T. Hanbicki, S. C. Erwin, C. S. Hellberg, J. M. Sullivan, J. E. Mattson,dagger T. F. Ambrose,ddagger A. Wilson,§ G. Spanos, B. T. Jonkerparallel

We report on the epitaxial growth of a group-IV ferromagnetic semiconductor, MnxGe1-x, in which the Curie temperature is found to increase linearly with manganese (Mn) concentration from 25 to 116 kelvin. The p-type semiconducting character and hole-mediated exchange permit control of ferromagnetic order through application of a ±0.5-volt gate voltage, a value compatible with present microelectronic technology. Total-energy calculations within density-functional theory show that the magnetically ordered phase arises from a long-range ferromagnetic interaction that dominates a short-range antiferromagnetic interaction. Calculated spin interactions and percolation theory predict transition temperatures larger than measured, consistent with the observed suppression of magnetically active Mn atoms and hole concentration.

Naval Research Laboratory, Washington, DC 20375, USA.
*   Present address: School of Physics and CSCMR, Seoul National University, Seoul 151-747, Korea.

dagger    Present address: Micron Technology, Boise, ID 33707, USA.

ddagger    Present address: Seagate Technology, Pittsburgh, PA 15203, USA.

§   Present address: Boeing Satellite Systems, El Segundo, CA 90009, USA.

parallel    To whom correspondence should be addressed. E-mail: jonker{at}nrl.navy.mil

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Science. ISSN 0036-8075 (print), 1095-9203 (online)