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O: Fachverband Oberflächenphysik

O 91: [MA] Poster II

O 91.25: Poster

Freitag, 30. März 2012, 11:00–14:00, Poster A

Slow Relaxation Effects in CMR Manganite Films and Superlattices — •Markus Jungbauer, Felix Koeth, Sebastian Hühn, Markus Michelmann, and Vasily Moshnyaga — I. Physikalisches Institut, Universität Göttingen

Colossal magnetoresistance (CMR) and complex magnetic/electric state close to the I. order phase (metal-insulator) transition in ferromagnetic perovskite manganites are still puzzling phenomena. We studied epitaxial films of ( La_1−yPr_y )_0.7Ca_0.3MnO₃/MgO(100) (y=0.4-0.6) with respect to their magnetotransport and magnetooptic properties with special focus on the relaxation effects. Close to the metal-to-insulator transition temperature, T_MI , application of magnetic field, B=0−1   T , leads to a relaxation of the electrical resistivity on a timescale, τ ≈ 100   s . Considering the observed temperature hysteresis of resistance and magnetization close to T_C as well as an anomalous increase of coercive field and low-field CMR in the vicinity of T_MI a following semi-quantitative picture of the complex magnetic state close to the phase transition was developed: the nanoscopic single-domain ferromagnetic clusters are coupled antiferromagnetically by a short-range-ordered correlated polaronic phase with a thickness of few monolayers. By growing digital (FMM/AFMCOI) _N superlattices with FMM=La_0.7(Ca,Sr)_0.3MnO₃ and AFMCOI=Pr_1−xCa_xMnO₃ (x=0.3-0.7) we try to reproduce and to tune this unique magnetic state with the main aim to obtain the enhanced low-field CMR close to room temperature. A financial support from EU FP7 via the Project IFOX (interfacing oxides) is acknowledged.