Strain-mediated phase coexistence in MnAs heteroepitaxial films on GaAs: An x-ray diffraction study

Abstract

The temperature-dependent phase coexistence between crystalline phases in heteroepitaxial films of MnAs on GaAs is studied. The epitaxial constraints on the film expansion are analyzed. The x-ray-diffraction data are fitted to a model of periodic elastic domains. The temperature dependencies of phase fractions, the domain sizes, and the misfits are simultaneously obtained. The domain sizes correspond to the minimum of elastic energy, which proves the equilibrium state of the heteroepitaxial system at each temperature.

Ferromagnetic nanoclusters formed by Mn implantation in GaAs

“…This coexistence can arise from a single nanostructure and/or a distribution of pure ␣-and ␤-phase nanostructures and its origin is still a subject of investigation. Both the coexistence and the hysteresis have been observed in previous works [10][11][12] on thin MnAs films grown on GaAs and were attributed to strain effects.…”

Epitaxial hybrid ferromagnet-semiconductor structures: growth, structural and magnetic properties

“…As a result of the epitaxial strain induced at the β → α phase transition, a striped phase separation occurs [17,21]. A self-organized pattern with a periodic array of ridges and grooves is observed at room temperature ( Fig.…”

“…At the β → α phase transition during cooling from growth to room temperature, the plane corresponding to (0001) of the α-phase expands discontinously by ≈1.2%, whereas the change along [0001] is comparatively small [20]. The epitaxial constraints of the film lead to an equilibrium coexistence between α-and β-MnAs over a wide temperature interval [17]. The phase composition of the films is obtained from ω-2θ x-ray diffraction scans which show two separate [1100] and (020) peaks for the α-and β-phase, respectively.…”

“…1). Two fundamental issues for understanding this unexpected result of real heteroepitaxy have been identified: (i) an interesting anisotropic lattice mismatch accommodation mechanism [16] and (ii) the strain-mediated coexistence of α-and β-MnAs below the bulk phase transformation temperature [17]. By controlling the stoichiometry of the GaAs template and the MnAs growth conditions, several epitaxial orientations can be realized [14,15].…”

Dynamics of the MnAs α/β-Striped Microstructure and of the Fe Magnetization Reversal in Fe/MnAs/GaAs(001): An Optical-Laser Pump–Free-Electron-Laser Probe Scattering Experiment

“…The period of the stripes, p, and the height of the steps between them, d, are determined by the MnAs layer thickness, t, with p~5 × t and d~1%-2% of t [7]. The period is almost temperature independent (this condition is not met at the extremes of the phase coexistence temperature region), and the relative width of α and β stripes within a period varies continuously with temperature [7,8].…”