Non-ferromagnetic Insulating Interface Region in La_0.14Pr_0.56Sr_0.3MnO_0.3/SrTiO₃ and La_0.7Ca_0.3MnO₃/Gd_0.7Ca_0.3MnO₃ Multilayers

La_0.14Pr_0.56Sr_0.3MnO₃/SrTiO₃ and La_0.7Ca_0.3MnO₃/Gd_0.7Ca_0.3MnO₃ multilayers have been fabricated by using pulsed laser deposition. The insulator--metal transition temperatures of the multilayers decrease with the decreasing thickness of the ferromagnetic layers. It is confirmed from the experiment and analysis that a non-ferromagnetic insulating region exists near the interface, which could not be attributed to the roughness of the growth surfaces and disorder of the ferromagnetic layers.