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

• 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-temperature (400 degrees C) and high-temperature (560 degrees C and 630 degrees C) annealing of (Ga,Mn)As layers with Mn concentrations between 0.1% and 2%, grown by molecular beam epitaxy at 270 degrees C. Decomposition of (Ga,Mn)As is already observed at the lowest annealing temperature of 400 degrees C 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% and 2% 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.

Subject headings

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

Keyword

TECHNOLOGY

TEKNIKVETENSKAP

Teknisk fysik med inriktning mot fasta tillståndets fysik

Engineering Science with specialization in Solid State Physics

molecular beam epitaxy

nanomagnetism

magnetic semiconductors

Publication and Content Type

ref (subject category)

art (subject category)