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Mixed-valence iron compounds are fascinating materials exemplified by ferrimagnetic Fe3O4, multiferroic LuFe2O4, and a pigment Fe4[Fe(CN)6]3. Mixed-valent iron (oxy)phosphates also provide a large variety of different connections between magnetic ions, which are responsible for complex magnetism. Fe7(PO4)6 (Fe32+Fe43+(PO4)6) has well-defined Fe2+ and Fe3+ sites and shows two antiferromagnetic transitions at TN1 = 47 K and TN2 = 16 K. Here, we investigated magnetic structures of Fe7(PO4)6 (at zero magnetic field) using neutron powder diffraction and constructed a temperature–magnetic-field phase diagram. Below TN1, magnetic propagation vector is k1 = (1/2, 0, 1/2), and magnetic moments on Fe3+ sites are nearly fully ordered; while moments on Fe2+ sites are significantly reduced. Below TN2, the second propagation vector appears k2 = (0, 1/2, 0) and co-exists with k1; moments on Fe2+ sites are fully ordered (at 2 K) reaching 4.5B suggesting noticeable spin-orbital contributions. Co-existence of two propagation vectors and triclinic symmetry result in variations of total magnetic moments on each site. Magnetic measurements up to 300 kOe detected one field-induced transition near 55.5 kOe. Data showed that TN1 is nearly magnetic-field independent up to 90 kOe, while a more complex behavior was observed near TN2 at magnetic fields around 50 kOe.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: magnetic structures, magnetic phase diagram, mixed valence, iron phosphates

刊行年月日: 2026-04-06

出版者: American Chemical Society (ACS)

掲載誌:

• Inorganic Chemistry (ISSN: 1520510X) vol. 65 issue. 13 p. 7418-7430

研究助成金:

• Japan Society for the Promotion of Science JP25K01657

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1021/acs.inorgchem.6c00534

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更新時刻: 2026-04-16 16:02:35 +0900

MDRでの公開時刻: 2026-04-16 18:27:27 +0900