Effect of Trapped Magnetic Flux on Neutron Scattering in La 1.85 Sr 0.15 CuO 4 Superconductor

The superconducting La 1.85 Sr 0.15 CuO 4 ceramics has been studied by small angle neutron scattering, magnetization measurements, and scanning electron microscopy. Experiments have shown that the intensity of the magnetic scattering is 2–3 times higher in the field cooled regime than in the zero-field cooled regime. Additional magnetic heterogeneities due to closure of the trapped magnetic flux cause the excess scattering in the field cooled regime. The isotropic nature of the scattering is associated with the absence of a preferred direction of the Abrikosov vortices, which is caused by the random orientation of the ab planes of the anisotropic superconductor granules.