Successful Enhancement of Magnetization in Iron Oxide (Black Rust) through Rare Earth Element Substitution

Magnetite (Fe₃O₄ ) is one of the most important magnetic materials and widely applied in various fields including spintronics, medicine, and catalytic chemistry. Recently, enhancement of the saturation magnetization has become an important issue for further functionalization of Fe₃O₄. In response to this, Yoshida et al. from our research group have employed computational nanomaterial design techniques to predict that the partial substitution of Fe with Eu in the Fe₃O₄ leads to a remarkable enhancement of the magnetization.

Here, the team controlled the substitution site of Eu by varying the growth rate of the Fe₃O₄  epitaxial thin films. It was found that the substitution of Fe by Eu at tetrahedral sites of the spinel structure in Fe₃O₄ results in the enhancement of the magnetization, consistent with the theoretical predictions of Yoshida et al. Furthermore, XMCD measurements revealed that the electron spins of Eu and Fe ions are ferromagnetically coupled. These findings are expected to contribute to significant advancements in the functionalities of Fe₃O₄-based magnet, chemical catalysts, spintronic devices and medical technologies in the future.

Papers
Journal: Small
Title: Noncollinear Magnetism in Fe3O4 Induced via Site-Selective Rare-Earth Substitution Boosting Its Saturation Magnetization
Authors: Haining Li, Masaki Kobayashi, Sonju Kou, Md Shamim Sarker, E M K Ikball Ahamed, Kohei Yamagami, Tetsuya Fukushima, Kaijie Ma, Shuting Ma, Takahito Takeda, Ryo Okano, M. Hussein N. Assadi, Hiroyasu Yamahara, Hiroshi Katayama-Yoshida, Hitoshi Tabata, and Munetoshi Seki*
DOI: 10.1002/smll.202411133