TY - JOUR
T1 - Embedded clustering in Cr-doped AlN
T2 - Evidence for general behavior in dilute magnetic III-nitride semiconductors
AU - Cui, X. Y.
AU - Fernandez-Hevia, D.
AU - Delley, B.
AU - Freeman, A. J.
AU - Stampfl, C.
N1 - Funding Information:
We acknowledge the computing resources provided by the Australian Partnership for Advanced Computing (APAC) National Facility and by the Australian Centre for Advanced Computing and Communications (AC3). We thank the Australian Research Council for financial support. Work at Northwestern University was supported by the NSF (through its MRSEC program).
Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2007
Y1 - 2007
N2 - 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.
AB - 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.
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U2 - 10.1063/1.2735405
DO - 10.1063/1.2735405
M3 - Article
AN - SCOPUS:34249882765
VL - 101
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 10
M1 - 103917
ER -