Berlin 2005 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 25: Si / Ge

HL 25.8: Vortrag

Samstag, 5. März 2005, 12:30–12:45, TU P-N226

Ferromagnetic Mn–doped Ge — •Thomas Vallaitis, Mario Gjukic, Christian Jäger, and Martin S. Brandt — Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching, Germany

Heavily manganese–doped germanium with a reported Curie temperature T_C of up to 116 K [Park et al., Science 295 (2002), 651] is of interest as a potential material for spintronic applications. Samples have been grown on Ge(100) substrates by MBE with manganese concentrations ranging from 0.02 at.% up to 52 at.%, as determined by elastic recoil detection analysis and EDX. The substrate temperature was approx. 225 ^∘C. Raman scattering and UV/VIS reflection measurements indicate a good crystalline quality of the epitaxial films up to a Mn concentration of 10 at.%, where the Ge TO Raman peak shows a FWHM of 5.4 cm⁻¹. Raman modes attributed to Mn–Mn vibrations as well as a low concentration of holes in Hall effect measurements indicate that clusters or intermetallic compounds are formed. SQUID magnetization measurements for samples with a Mn concentration of 3−20 at.% clearly show the presence of several magnetic phases: (i) the ferromagnetic Mn₅Ge₃ with T_C=285 K and (ii) a low–temperature phase with a remanence that disappears at 30 K.