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

Area of Science:

• Materials Science
• Condensed Matter Physics
• Surface Science

Background:

• Investigating interfacial phenomena in complex oxide heterostructures is crucial for understanding emergent electronic and magnetic properties.
• La0.7Ca0.3MnO3 (LCMO) and LaNiO3 (LNO) are perovskite oxides exhibiting distinct electronic and magnetic behaviors.

Purpose of the Study:

• To elucidate the mechanism behind the significant magnetic coupling observed at the LCMO/LNO interface.
• To understand the role of charge transfer and orbital reconstruction in mediating interfacial magnetism.

Main Methods:

• Utilizing X-ray Photoelectron Spectroscopy (XPS) to probe the electronic structure across the LCMO/LNO interface.
• Analyzing core-level spectra (Mn 2p) to identify charge states and electronic transitions.

Main Results:

• Observed a continuous shift of the Fermi level across the interface region.
• Identified charge transfer between Mn and Ni ions (Mn(3+)-Ni(3+) → Mn(4+)-Ni(2+)) mediated by oxygen vacancies.
• Detected a characteristic
• shoulder feature
• in Mn 2p spectra, indicative of itinerant electrons.
• Mapped orbital reconstruction based on Fermi level position and charge transfer dynamics.

Conclusions:

• The interfacial charge transfer and subsequent orbital reconstruction are key to the observed magnetic coupling.
• Ferromagnetic interactions between Ni(2+) and Mn(4+) ions likely pin the ferromagnetic LCMO, establishing the magnetic coupling at the interface.