Author: ["T. Kawakami","Y. Tsujimoto","H. Kageyama","Xing-Qiu Chen","C. L. Fu","C. Tassel","A. Kitada","S. Suto","K. Hirama","Y. Sekiya","Y. Makino","T. Okada","T. Yagi","N. Hayashi","K. Yoshimura","S. Nasu","R. Podloucky","M. Takano"]
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Abstract
Spin transition has attracted the interest of researchers in various fields since the early 1930s, with thousands of examples now recognized, including those in minerals and biomolecules. However, so far the metal centres in which it has been found to occur are almost always octahedral six-coordinate 3d4 to 3d7 metals, such as Fe(II). A five-coordinate centre is only rarely seen. Here we report that under pressure SrFe(II)O2, which features a four-fold square-planar coordination, exhibits a transition from high spin (S = 2) to intermediate spin (S = 1). This is accompanied by a transition from an antiferromagnetic insulating state to a ferromagnetic so-called half-metallic state: only half of the spin-down (dxz,dyz) states are filled. These results highlight the square-planar coordinated iron oxides as a new class of magnetic and electric materials. Spin transitions — metal ions changing from high- to low-spin states — can be triggered by a range of stimuli and have normally only been observed in octahedrally coordinated ions. Now, a four-coordinate, square-planar iron(II) compound, SrFeO2, exhibits such a spin transition, accompanied by a transition from an antiferromagnetic insulator to a ferromagnetic half-metal. Cite this article
Kawakami, T., Tsujimoto, Y., Kageyama, H. et al. Spin transition in a four-coordinate iron oxide. Nature Chem 1, 371–376 (2009). https://doi.org/10.1038/nchem.289 