Distinct local electronic structure and magnetism for Mn in amorphous Si and Ge

Li Zeng, J. X. Cao, E. Helgren, J. Karel, E. Arenholz, Lu Ouyang, David Smith, R. Q. Wu, F. Hellman

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Abstract

Transition metals such as Mn generally have large local moments in covalent semiconductors due to their partially filled d shells. However, Mn magnetization in group-IV semiconductors is more complicated than often recognized. Here we report a striking crossover from a quenched Mn moment (<0.1 μB) in amorphous Si (a-Si) to a large distinct local Mn moment (≥3 μB) in amorphous Ge (a-Ge) over a wide range of Mn concentrations (0.005-0.20). Corresponding differences are observed in d -shell electronic structure and the sign of the Hall effect. Density-functional-theory calculations show distinct local structures, consistent with different atomic density measured for a-Si and a-Ge, respectively, and the Mn coordination number Nc is found to be the key factor. Despite the amorphous structure, Mn in a-Si is in a relatively well-defined high coordination interstitial type site with broadened d bands, low moment, and electron (n -type) carriers, while Mn in a-Ge is in a low coordination substitutional type site with large local moment and holes (p -type) carriers. Moreover, the correlation between N c and the magnitude of the local moment is essentially independent of the matrix; the local Mn moments approach zero when Nc >7 for both a-Si and a-Ge.

Original languageEnglish (US)
Article number165202
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume82
Issue number16
DOIs
StatePublished - Oct 14 2010

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Zeng, L., Cao, J. X., Helgren, E., Karel, J., Arenholz, E., Ouyang, L., Smith, D., Wu, R. Q., & Hellman, F. (2010). Distinct local electronic structure and magnetism for Mn in amorphous Si and Ge. Physical Review B - Condensed Matter and Materials Physics, 82(16), [165202]. https://doi.org/10.1103/PhysRevB.82.165202