AC losses in untwisted "in situ" superconductors above the percolation threshold

Magnetization measurements in the low frequency ac magnetic field for untwisted in situ prepared superconducting Cu-Nb composites are presented. Wires with various degrees of drawing deformation were examined. Penetration depth in the low field region increases with the deformation of the sample. Behavior of the magnetization curves is analyzed on the basis of a simple critical state model allowing for the suppression of screening currents in high magnetic fields. Agreement of the model with the experimental data is discussed.