Anisotropic Ginzburg-Landau model was systematically tested in Nbt(Nb) and Nbt(Nb)/Cu5nm/Co40nm (t(Nb) = 20 and 100 nm) films. A Delta T-C-parameter was defined as a temperature difference between the critical temperatures determined for in-plane and out-of-film plane field configurations (Delta T-C = T-C perpendicular to C - T-C parallel to C). The Delta T-C behavior for Nb (20 nm) and Nb(20 nm)/Co(40 nm) films shows a linear increase with applied field concomitantly with the increase of magnetization values in the out-of-film plane configuration. The stray field of ferromagnetic Co layer was determined in the zero field case to be (7 +/- 2) mT, while a variation ratio between the stray field and the applied field ((dB(Co)/dB) of the Co layer was calculated to be (-0.22 +/- 0.02). Our results bring)contributions to clarify proximity and magnetostatic effects; issues that still need to be comprehended for superconducting spin valve technological applications.