Abstract
A novel proximity effect between high-Tc superconductor and magnetic manganese oxide has been found. Supercurrents were observed through La 0.7Ca 0.3MnO z (LCMO) magnetic barrier as thick as 500 nm in YBCO/LCMO/YBCO trilayered junctions. We confirmed this proximity effect in coplanar-type junctions with spacing of 200 nm, and presented a possibility that this phenomenon occurs between NbN and LCMO. Furthermore we investigated current-voltage (I–V) characteristics and magnetic properties for Y 1Ba 2Cu 3O y/La 1−xSr xMnO z(200nm)/Y 1Ba 2Cu 3O y (YBCO/LSMO/YBCO) junctions. I–V characteristics changed systematically with varying the magnetism of the barrier. When x value was 0.2, super-currents passed through the barrier, and it was found that ferromagnetism (Ms= 135 emu/ cc) and supercurrents coexist in this proximity state. Magnetism of the LSMO is understood as a complicated and fluctuated state of ferromagnetic coupling in ab plane and antiferromagnetic coupling along c-axis. Considering supercurrents passed through the La 1−xSr x(Mn 3+ 1−xMn 4+ x)O z along c-axis, our results suggest a novel proximity effect mechanism, that is antiferromagnetic spin fluctuation and charge fluctuation can transport Cooper-pairs over a long range.
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