Regensburg 2010 – scientific programme

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MA: Fachverband Magnetismus

MA 19: Magnetic Half-metals and Oxides II

MA 19.6: Talk

Wednesday, March 24, 2010, 16:30–16:45, H22

Ultrasound velocity of CMR manganites at the phase transition — •Markus Michelmann, Walter Arnold, Vasily Moshnyaga, and Konrad Samwer — I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37707 Göttingen

Perovskite (La, Pr, Ca)MnO₃ manganites attract great attention due to colossal magnetoresistance (CMR), strong electron-phonon-coupling and electronic phase-separation. Here we studied elastic properties of polycrystalline (La_1−yPr_y)_0.7Ca_0.3MnO₃ bulk samples by means of ultrasound velocity measurement (at ∼5MHz) as a function of temperature (T = 20−300K) and magnetic field (B = 0−5T). The sound velocity drops near the M-I-transition by ∼3% in a single step but changes its shape with applied magnetic field (B > 2T). The results of the elastic properties look first like a CMR-behaviour indicating a significant structural modification. However, in higher fields the nature of the transition seems to vary. The results will be compared with specific heat and magnetization measurements for the same CMR compounds.
Support by Deutsche Forschungsgemeinschaft via SFB 602, TP A2 is acknowledged.