We show that ferromagnetic/paramagnetic La 0.75Sr 0.25MnO 3/LaNiO 3 multilayers present an unexpected magnetic exchange-bias effect (EBE), observed in field-cooled magnetization loops. The exchange-bias field and the enhancement of the coercivity vanish around 50 K. We demonstrate that the oxidation state of the Ni and Mn cations changes from Mn3 +-Ni3 + to Mn4 +-Ni2 + in the layers close to the interface probed by x-ray absorption spectroscopy measurements. The variation of the valence states is accompanied by a change in the magnetic behavior of the cations at the La 0.75Sr 0.25MnO 3/LaNiO 3 interface, possibly giving rise to the formation of magnetic or magnetically frustrated regions that may pin the ferromagnetic La 0.75Sr 0.25MnO 3 layers and explain the EBE. © 2012 American Physical Society.