Oxygen Vacancy-Induced Correlation and Enhanced Magnetism in SrRuO₃ Nanoparticles Studied by X-ray Spectroscopic Techniques

Abstract

We report a comprehensive study of the electronic structure and magnetic properties of SrRuO₃ (SRO) nanoparticles synthesized via the co-precipitation method. Synchrotron-based X-ray photoemission and absorption spectroscopies, including resonant photoemission spectroscopy (RPES), X-ray absorption spectroscopy (XAS), and X-ray magnetic circular dichroism (XMCD), reveal the presence of correlated Ru 4d electrons near the Fermi level. Both the valence-band and conduction-band spectra show dominant incoherent spectral weight, indicating the partial localization of Ru-4d states. The incoherent feature is attributed to the O 2p screening of Ru 4d orbitals at 1.9 eV in the valence band. The nanoparticles exhibit robust ferromagnetism at 70 K, with spin and orbital magnetic moments ranging from 1.23 to 2.23 μB/Ru and from 0.09 to 0.14 μB/Ru, respectively, under external magnetic fields of 0.1–3 T. The observed enhancement in the magnetic moments is attributed to oxygen-vacancy-induced localization, consistent with a correlated metallic ground state in the positive charge-transfer-energy regime. These findings highlight the crucial role of non-stoichiometry in tuning the electronic correlations and magnetic behavior of SRO, underscoring its potential for oxide-based spintronic applications.