Interfacial Charge Transfer and Emergent Ferromagnetism in CaMnO₃/NdNiO₃ Superlattices

We investigate superlattices composed of the antiferromagnetic insulator CaMnO₃ and the correlated oxide NdNiO₃, which undergoes a temperature-driven metal–insulator transition accompanied by antiferromagnetic ordering. Using a combination of hard X-ray photoelectron spectroscopy (HAXPES), soft X-ray standing-wave photoemission spectroscopy (SW-XPS), and X-ray magnetic circular dichroism (XMCD), we obtain element‐ and depth-resolved information on the electronic and magnetic structure throughout the heterostructure. Our measurements reveal interfacial charge transfer leading to an enhanced concentration of Mn³⁺ cations in the interfacial regions of CaMnO₃. This redistribution of electronic charge promotes ferromagnetic alignment through the Mn⁴⁺–Mn³⁺ double-exchange interaction, giving rise to interfacial ferromagnetism. These findings demonstrate a route to controlling localized magnetic states in correlated oxides for potential use in spintronic devices, magnetic memory, and oxide-based logic architectures.