Formation process and superparamagnetic proberties of (Mn,Ga)As nanocrystals in GaAs fabricated by annealing of (Ga,Mn)As layers with low Mn content

Sadowski,J.; Kovacs, Andras; Dietl,T.; Domagala,J.; Dunin-Borkowski, Rafal; Mathieu,R.; Kasama,T.

doi:10.1103/PhysRevB.84.245306

Journal Article

FZJ-2013-00877

Formation process and superparamagnetic proberties of (Mn,Ga)As nanocrystals in GaAs fabricated by annealing of (Ga,Mn)As layers with low Mn content

Sadowski,J. (Corresponding author) ; Domagala,J. ; Mathieu,R. ; Kovacs, A.FZJ* ; Kasama,T. ; Dunin-Borkowski, R.FZJ* ; Dietl,T.

2011
APS College Park, Md.

Physical review / B 84(24), 245306 (2011) [10.1103/PhysRevB.84.245306]

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Please use a persistent id in citations: http://hdl.handle.net/2128/4963 doi:10.1103/PhysRevB.84.245306

Abstract: X-ray diffraction, transmission electron microscopy, and magnetization measurements are employed to study the structural and magnetic properties of Mn-rich (Mn,Ga)As nanocrystals embedded in GaAs. These nanocomposites are obtained by moderate (400C) and high temperature (560 and 630C) annealing of (Ga,Mn)As layers with Mn concentrations between 0.1 and 2%, grown by molecular beam epitaxy at 270oC. Decomposition of (Ga,Mn)As is already observed at the lowest annealing temperature of 400C for layers with initial Mn content of 1% and 2%. Both cubic and hexagonal (Mn,Ga)As nanocrystals, with similar diameters of 7 - 10 nm are observed to coexist in layers with an initial Mn content of 0.5% after higher temperature annealing. Measurements of magnetization relaxation in the time span 0.1 - 10 000 s provide evidence for superparamagnetic properties of the (Mn,Ga)As nanocrystals, as well as for the absence of spin-glass dynamics. These findings point to weak coupling between nanocrystals even in layers with the highest nanocrystal density.

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