Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 52: Poster II - Magnetic Heusler compounds, Magnetic shape memory alloys, Thin Films, Micro-/Nano-structured magnetic materials, Graphene, Spins in organics, Magnetic imaging, Surface Magnetism, Spin excitations/Torque, Spincaloric transport
MA 52.25: 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 ( La1−yPry )0.7Ca0.3MnO3/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, TMI , 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 TC as well as an anomalous increase of coercive field and low-field CMR in the vicinity of TMI 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=La0.7(Ca,Sr)0.3MnO3 and AFMCOI=Pr1−xCaxMnO3 (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.