Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)

MA 15.93: Poster

Dienstag, 27. März 2007, 15:00–19:00, Poster A

Heterogeneous mixed valence of a Sm/Gd(0001) monolayer revealed by scanning tunneling spectroscopy — •Daniel Wegner and Günter Kaindl — Freie Universität Berlin, Institut für Experimentalphysik, Arnimallee 14, 14195 Berlin

Many photoelectron spectroscopy studies show that low coverages of the lanthanide metal Samarium on various substrates are mostly mixed-valent. Due to the spatial averaging of this technique, the nature of the mixed valence -- whether it is homogeneous or heterogeneous -- could not be shown directly. Moreover, a lot of effort is necessary to rule out artifacts, e.g. structural disorder and nonuniform layer or island growth. We show that STS of a well-ordered monolayer of Sm on a Gd(0001) substrate proves a heterogeneous mixed valence, while islands of a second layer are divalent. The determination by STS is possible, because the Sm monolayer exhibits a localized surface state that indicates the valence state indirectly through a splitting. The results can be understood by comparison with STS on Sm(0001) and on Eu/Gd(0001).