The onset of ferromagnetism and superconductivity in [La0.7Sr0.3MnO3(n u.c.)/YBa2Cu3O7(2 u.c.)]20 superlattices

Fermi level shifting, charge transfer and induced magnetic coupling at La0.7Ca0.3MnO3/LaNiO3 interface

A large magnetic coupling has been observed at the La_0.7Ca_0.3MnO₃/LaNiO₃ (LCMO/LNO) interface. The x-ray photoelectron spectroscopy (XPS) study results show that Fermi level continuously shifted across the LCMO/LNO interface in the interface region. In addition, the charge transfer between Mn and Ni ions of the type Mn³⁺ − Ni³⁺ → Mn⁴⁺ − Ni²⁺ with the oxygen vacancies are observed in the interface region. The intrinsic interfacial charge transfer can give rise to itinerant electrons, which results in a “shoulder feature” observed at the low binding energy in the Mn 2p core level spectra. Meanwhile, the orbital reconstruction can be mapped according to the Fermi level position and the charge transfer mode. It can be considered that the ferromagnetic interaction between Ni²⁺ and Mn⁴⁺ gives rise to magnetic regions that pin the ferromagnetic LCMO and cause magnetic coupling at the LCMO/LNO interface.