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Enhancement of the Critical Current Densities and Trapped Flux of Gd-Ba-Cu-O Bulk HTS Doped With Magnetic Particles

For bulk HTS rotating machines, enhancement of the trapped flux is a crucial task to achieve practical applications with high torque density. The increase of critical current density Jc using artificial pinning centers is an efficient technique for the enhancement of the flux trapping properties. We attempted to enhance both Jc and the trapped flux in bulk HTS with magnetic/ferromagnetic particles additions. Fe-B-Si-Nb-Cr-Cu amorphous alloy, Fe2O3 and CoO particles were introduced into the Gd123 matrix. The melt growth of the single-domain bulks with different magnetic particles was performed in air. Enhancement of the critical current density Jc at 77 K was derived in the bulks with Fe2O3 and Fe-B-Si-Nb-Cr-Cu additions, while the superconducting transition temperature of 93 K was not degraded significantly. The experiment of the magnetic flux trapping was then conducted under static magnetic field magnetization with liquid nitrogen cooling. In the bulk with 0.4 mol% of Fe-B-Si-Nb-Cr-Cu, the integrated trapped flux exceeds over 35% compared to the one without magnetic particle addition. On the other hand, the addition of CoO particles resulted in a reduction of both Jc and trapped magnetic flux. Present results indicate that the introduction of magnetic particles gives a significant effect to the flux pinning performance.