Charge-transfer-induced interfacial ferromagnetism and its impact on the exchange bias effect in La 0.7 Sr 0.3 MnO 3 /NdNiO 3 correlated oxide heterostructures were investigated by soft x-ray absorption and x-ray magnetic circular dichroism spectra in a temperature range from 10 to 300 K. Besides the antiferromagnetic Ni 3+ cations which are naturally part of the NdNiO 3 layer, Ni 2+ ions are formed at the interface due to a charge-transfer mechanism involving the Mn element of the adjacent layer. They exhibit a ferromagnetic behavior due to the exchange coupling to the Mn 4+ ions in the La 0.7 Sr 0.3 MnO 3 layer. This can be seen as detrimental to the strength of the unidirectional anisotropy since a significant part of the interface does not contribute to the pinning of the ferromagnetic layer. By analyzing the line-shape changes of the x-ray absorption at the Ni L 2,3 edges, the metal-insulator transition of the NdNiO 3 layer is resolved in an element-specific manner. This phase transition is initiated at about 120 K, way above the paramagnetic to antiferromagnetic transition of the NdNiO 3 layer which measured to be 50 K. Exchange bias and enhanced coercive fields were observed after field cooling the sample through the Néel temperature of the NdNiO 3 layer. Different from La 0.7 Sr 0.3 MnO 3 /LaNiO 3 , the exchange bias observed in La 0.7 Sr 0.3 MnO 3 /NdNiO 3 is due to the antiferromagnetism of NdNiO 3 and the frustration at the interface. These results suggest that reducing the interfacial orbital hybridization may be used as a tunable parameter for the strength of the exchange bias effect in all-oxide heterostructures which exhibit a charge-transfer mechanism.

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