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Surface characterization of Mn(x)Ge(1−x) and Cr(y)Mn(x)Ge(1−x−y) dilute magnetic semiconductors

AuthorsGambardella, Pietro; Claude, L.; Rusponi, S.; Franke, K. J.; Brune, H.; Raabe, J.; Nolting, F.; Bencok, Peter; Hanbicki, A. T.; Jonker, B. T.; Grazioli, C.; Veronese, M.; Carbone, Carlo
KeywordsManganese compounds
Chromium compounds
Semimagnetic semiconductors
Ferromagnetic materials
Paramagnetic materials
Magnetic moments
X-ray photoelectron spectra
X-ray absorption
Semiconductor epitaxial layers
Surface composition
Magnetic circular dichroism
Issue Date28-Mar-2007
PublisherAmerican Physical Society
CitationPhysical Review B 75(12): 125211 (2007)
AbstractWe have used x-ray photoemission electron microscopy (XPEEM) and x-ray absorption spectroscopy (XAS) to characterize Mn(x)Ge(1−x) and Cr(y)Mn(x)Ge(1−x−y) films grown by molecular beam epitaxy. The surface layers of the as-grown films probed by XPEEM present segregation of Mn-rich phases. XAS using both total electron yield and fluorescence yield detection shows that the films are heavily oxidized after exposure to air. Etching in HF and HCl can be used to reduce oxidation, but inhomogeneities in the surface composition might not be completely eliminated depending on the Mn concentration. X-ray magnetic circular dichroism (XMCD) measurements reveal that neither the etched nor the as-grown films present remanent ferromagnetic behavior down to a temperature of 5 K within the probing depth of the fluorescence yield (~20 nm). Mn is paramagnetic in both the oxidized and etched samples, with an increased tendency to order magnetically toward the interior of the films. Cr in Cr(y)Mn(x)Ge(1−x−y) possesses a paramagnetic moment only in the oxidized form. A comparison of the XAS line shapes obtained in the present study with those of Mn impurities deposited on Ge and GaAs surfaces demonstrates that the interpretation of XAS spectra of Mn-doped dilute magnetic semiconductors in the literature is often affected by residual oxidation.
Description7 pages, 7 figures.-- PACS nrs.: 75.50.Pp; 75.70.-i; 78.70.Dm; 75.20.Hr.
Publisher version (URL)http://dx.doi.org/10.1103/PhysRevB.75.125211
Appears in Collections:(CIN2) Artículos
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