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dc.contributor.authorGambardella, Pietro-
dc.contributor.authorClaude, L.-
dc.contributor.authorRusponi, S.-
dc.contributor.authorFranke, K. J.-
dc.contributor.authorBrune, H.-
dc.contributor.authorRaabe, J.-
dc.contributor.authorNolting, F.-
dc.contributor.authorBencok, Peter-
dc.contributor.authorHanbicki, A. T.-
dc.contributor.authorJonker, B. T.-
dc.contributor.authorGrazioli, C.-
dc.contributor.authorVeronese, M.-
dc.contributor.authorCarbone, Carlo-
dc.identifier.citationPhysical Review B 75(12): 125211 (2007)en_US
dc.description7 pages, 7 figures.-- PACS nrs.: 75.50.Pp; 75.70.-i; 78.70.Dm; 75.20.Hr.en_US
dc.description.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.en_US
dc.description.sponsorshipPart of this work was performed at the Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland. The work at Naval Research Laboratory was supported by the Office of Naval Research. Financial support from the Swiss National Science Foundation (Grant No. 21-63864) and the Italian Ministero dell’Istruzione, dell’Università e della Ricerca (FIRB project "Nanotecnologie e nanodispositivi optoelettronici, elettronici e spintronici") is gratefully acknowledged.en_US
dc.format.extent849828 bytes-
dc.publisherAmerican Physical Societyen_US
dc.subjectManganese compoundsen_US
dc.subjectChromium compoundsen_US
dc.subjectSemimagnetic semiconductorsen_US
dc.subjectFerromagnetic materialsen_US
dc.subjectParamagnetic materialsen_US
dc.subjectMagnetic momentsen_US
dc.subjectX-ray photoelectron spectraen_US
dc.subjectX-ray absorptionen_US
dc.subjectSemiconductor epitaxial layersen_US
dc.subjectSurface compositionen_US
dc.subjectMagnetic circular dichroismen_US
dc.titleSurface characterization of Mn(x)Ge(1−x) and Cr(y)Mn(x)Ge(1−x−y) dilute magnetic semiconductorsen_US
dc.description.peerreviewedPeer revieweden_US
dc.contributor.funderSwiss National Science Foundation-
dc.contributor.funderMinistero dell'Istruzione, dell'Università e della Ricerca-
dc.contributor.funderOffice of Naval Research (US)-
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