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Phys. Rev. B 75, 201201(R) (2007) [4 pages]

Dopant segregation and giant magnetoresistance in manganese-doped germanium

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A. P. Li1,2, C. Zeng3, K. van Benthem1,2, M. F. Chisholm2, J. Shen1,2, S. V. S. Nageswara Rao4,5, S. K. Dixit4, L. C. Feldman2,4,5, A. G. Petukhov6, M. Foygel6, and H. H. Weitering2,3
1Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
2Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
3Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
4Interdisciplinary Program in Materials Science, Vanderbilt University, Nashville, Tennessee 37235, USA
5Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA
6Physics Department, South Dakota School of Mines and Technology, Rapid City, South Dakota 57701, USA

Received 18 April 2007; published 10 May 2007

Dopant segregation in a MnxGe1−x dilute magnetic semiconductor leads to a remarkable self-assembly of Mn-rich nanocolumns, embedded in a fully compensated Ge matrix. Samples grown at 80 °C display a giant positive magnetoresistance that correlates directly with the distribution of magnetic impurities. Annealing at 200 °C increases Mn substitution in the host matrix above the threshold for the insulator-metal transition, while maintaining the columnar morphology, and results in global ferromagnetism with conventional negative magnetoresistance. The qualitative features of magnetism and transport in this nanophase material are thus extremely sensitive to the precise location and distribution of the magnetic dopants.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.75.201201
DOI:
10.1103/PhysRevB.75.201201
PACS:
75.50.Pp, 61.72.−y, 73.50.Jt, 75.47.De
 
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