In this investigation, we deposited multilayers of [(La 0.67 Sr 0.33 MnO 3 ) d /(YBa 2 Cu 3 O y ) x ], [(La 0.7 Ca 0.3 MnO 3 ) 4 /(YBa 2 Cu 3 O 7 ) x ] 180nm and [(La 0.45 Ca 0.55 MnO 3 ) 4 /(YBa 2 Cu 3 O 7 ) x ] 180nm of varying individual layer thicknesses using the ‘eclipse’ pulsed laser deposition technique. Transport measurements were performed to obtain the films’ critical temperatures (T c ). We study the interaction between superconductivity and magnetism within these heterostructures, paying attention to the superconducting and ferromagnetic coherence lengths, ξ F and ξ S respectively, of the materials in the system, and analyzing how these parameters affect the suppression of T c , eliminating stray field as a possible cause of T c suppression. We compared our data to previous work to achieve a more comprehensive study of oxide F/S multilayers. We observe that the magnetic nature of the manganite layers do not have much influence on T c suppression in the multilayers. We show that within certain limits, the thicknesses of both the superconducting and ferromagnetic layers individually affect the T c of the multilayers. The critical thickness of YBCO in our multilayers was estimated to be ∼20nm.