Detailed Elaboration Method and Magnetic Study of Nanometrical YBCO/YIG System

The blending of magnetic elements or compounds into a superconducting matrix has a direct effect on the physical properties of the latter and provides precious information on the superconductivity mechanisms, the spin/vortex interaction and the vortex pinning. To our knowledge, no study of the addition of nanoparticles of yttrium iron garnet Y3Fe5O12 (called commonly YIG) in the yttrium, barium and copper oxide YBa2Cu3O7−δ (well known under the YBCO appellation) nanometrical matrix has been performed up to the present time. The YBCO and YIG powders have been elaborated by a conventional ceramic process. The obtained products have been characterized by magnetization measurements, X-ray diffraction and optical microscopy. The used ways to reduce their grain sizes below 50 nm and to mix them avoiding the formation of grain crowds have been explained. Their nanometrical sizes have been confirmed by atomic force microscope analysis. Eight pellets have been elaborated. The thermal variations of zero field cooled magnetizations, in a residual field of 44 G, have shown that the introduction of 5 and 9% in weight of a non-superconductor material (YIG) into a superconducting matrix (YBCO) has reduced the TC only by 1 K for a ybcoyig5% pellet and 1.57 K for a ybcoyig9% one, comparatively with the ybcopur reference pellet’s TC. In another way, our results have shown that the incorporation of YIG in very low quantities, between 0 and 0.5% in weight of YIG, increases the value of the critical current JC of a ybcopur pellet (and, so, the vortex pinning). By fitting our experimental points starting from 0.5% in weight of YIG, an empirical law of the JC variation versus added YIG percentage is suggested.