Space-Charge Modulation of Antiferromagnetic-Ferromagnetic Core-Shell Magnetism in Ruthenium Nanoparticles.

Ding, Fei; Liu, Shilong; Guo, Shuxin; Wang, Haonan; Zhang, Leqing; Zhou, Lang; Sun, Huaze; Liu, Haining et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Here we report antiferromagnetic-ferromagnetic core-shell magnetism in electrochemically synthesized elemental ruthenium nanoparticles. The core exhibits strong antiferromagnetic interactions, while uncompensated surface spins drive emergent ferromagnetism. This is evidenced by a large negative Weiss constant (-72.5 K), nonsaturating magnetization at high fields, and temperature-dependent coercivity reaching 430 Oe at 2 K, a value 3 times larger than that reported for ferromagnetic ruthenium films. By employing space-charge engineering to modulate the surface electron density, we achieve reversible magnetization changes up to 46% at room temperature. Furthermore, significant voltage-dependent coercivity changes at low temperatures provide strong support for the direct modulation of surface ferromagnetism and hint at a tight coupling to the antiferromagnetic core. These results uncover distinctive magnetism in ruthenium nanoparticles and establish space-charge engineering as a general route to voltage-controlled magnetism in metallic nanomaterials, advancing antiferromagnetic spintronics.