We investigated the ac loss properties of a YBCO superconducting tape fabricated by IBAD-PLD technique. The YBCO layer is 0.5 μm thick. We measured the ac losses by a pickup coil method at 77 and 64 K using 3- and 6-tape stacks in addition to a single tape, where the tapes were arranged in the vertical direction to the wide surface. Sample tapes with a length of 60 mm were inserted into a saddle-shaped pickup coil and rotated around the central axis. The ac loss for the larger amplitude than the effective penetration field into the center of a tape was independent of the number of stacked tapes and proportional to the projective width in the direction of applied magnetic field. On the other hand, the ac loss for the small amplitude depended strongly on the number of stacked tapes due to the demagnetization effect. In addition we estimated the magnetic field dependence of the critical current density from the observed magnetization curves and also discussed on the origin of the anisotropy in ac loss property.
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