Preparation and properties of Eu-Ba-Cu-O superconducting bulk magnets for NMR application

We have investigated the fabrication and the superconducting and field trapping properties of large melt-textured Eu-Ba-Cu-O bulk superconductors for the purpose of application as a compact NMR magnet. We successfully fabricated c-axis oriented single-grain bulk samples up to 65 mm in diameter by melt-processing under a low oxygen partial pressure. The samples of 33 and 47 mm diameters could trap magnetic fields of 1.4 and 1.7 T at 77 K, respectively. The position dependence of Tc in the sample of 33mm diameter is very small throughout the sample. In 65 mm-sized sample, however, Tc and Jc lowered in inner region of the sample, leading to lowering of maximum trapped field. Trapped magnetic field was improved with keeping for long time at maximum temperature in melt-processing.