Embedded clustering in Cr-doped AlN: Evidence for general behavior in dilute magnetic III-nitride semiconductors

X. Y. Cui*, D. Fernandez-Hevia, B. Delley, A. J. Freeman, C. Stampfl

*Corresponding author for this work

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39 Scopus citations

Abstract

We report a systematic density-functional theory investigation of the "structure-property relationship" of Cr:AlN by doping up to 5 Cr atoms in large supercells, for which exhaustive structural and magnetic configurations have been calculated-including full atomic relaxation. Our results demonstrate that the Cr atoms tend to segregate to form Cr-N-Cr bonded clusters, which are embedded in the AlN host wurtzite structure. Significantly, while the ferromagnetic state with a spin moment close to 3 μB Cr is the ground state for both isolated "single" and "pair" doping configurations, for larger cluster configurations states containing antiferromagnetic or ferrimagnetic coupling with net spin in the range of 0-1.53 μB Cr are found to be energetically more favorable. Electrical conductivity (half-metallic or insulating) is predicted to be sensitively dependent on the dopant concentration. We propose a picture that various sized Cr-N-Cr bonded clusters coexist and the statistical distribution and associated magnetic properties will depend sensitively on the growth conditions. Such a scenario is in agreement with recent experiments and can help understand a number of hitherto puzzling experimental observations, notably the low mean saturation magnetic moment, the contracted lattice constants, and the highly insulating behavior.

Original languageEnglish (US)
Article number103917
JournalJournal of Applied Physics
Volume101
Issue number10
DOIs
StatePublished - 2007

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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