Magnetic properties of superconducting YBa₂Cu₃O _x permanent magnets prepared by the melt process

Demagnetizing curves after field cooling were measured in the melt processed YBa₂Cu₃O_x superconductors using a vibrating sample magnetometer and a SQUID magnetometer. The curves showed that the samples worked as strong bulk permanent magnets. This is attributed to the strong flux pinning of the bulk superconductors and is well explained in terms of the Bean-London model. The magnetic properties of the permanent magnet can be continuously changed using the field-cooling technique. The magnet properties of the melt-powder-melt-growth processed YBa₂Cu₃O _x with 1.5 mm thickness obtained at 5 K after field cooling in 10 kOe are as follows: the residual flux densities B_r are 9.6 kG (H∥ c) and 8.5 kG (H⊥ c); the coercive forces _bHc are 33 kOe (H∥ c) and 17 kOe (H⊥ c); and the maximum energy product, (BH) _max, are 110 MGOe (H∥ c) and 49 MGOe (H⊥ c).