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 15.4: Poster

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

Scanning tunneling spectroscopy on La_0.75Ca_0.25MnO₃ thin films in external magnetic fields — •Sigrun A. Köster, Thomas Mildner, Vasily Moshnyaga, Bernd Damaschke, and Konrad Samwer — I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

Perovskite manganites show the most intriguing and still far from understanding colossal magnetoresistance effect (CMR). The main effect is observed at the temperature induced transition from a ferromagnetic metallic to an insulating behavior. According to the percolation model of Dagotto et al.[1] two different phases, an insulating and conducting one, exist in parallel and lead to a percolative phase transition, the CMR. This coexistence is expected to depend on different material parameters, since the properties of manganites are very sensitive to lattice strain (e.g. Jahn-Teller strain) and disorder. We are able to very precisely tune the microstructure of our samples by the metallorganic aerosol deposition (MAD) technique. In our work we can show by scanning tunneling spectroscopy, that low resistivity and high resistivity regions exist in the samples, depending on the microstructure of the films, temperature and magnetic fields. Our study is aimed at achieving a more detailed picture of these electronic phases. Particularly we concentrated on STS measurements in magnetic fields at the transition temperature. This project was partially supported by the DFG in the course of SFB 602 Project A2.

[1] E. Dagotto, T. Hotta, A. Moreo, Physics Reports 344, (2001)