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Séminaire Magnétisme non conventionnel

Jeudi 13 Février à 14h00,
Salle Remy Lemaire, K223

Orateur : Christopher D. Ling (Univ. of Sydney, Australia)
"Fe4Si2Sn7O16 : a “Partial” Spin-liquid Candidate on a Kagomé Lattice"

Abstract

The compound Fe4Si2Sn7O16 has a unique crystal structure, consisting of ionic oxide layers based on edge-sharing FeO6 and Sn4+O6 octahedra alternating with layers of intermetallic character based on FeSn2+6 octahedra, separated by covalent SiO4 tetrahedra. [1,2] The ionic layers contain kagomé lattices of magnetic Fe2+ cations (octahedral crystal field, high-spin [HS] d6, S = 2) with perfect trigonal symmetry ; while the intermetallic “stannide” layers contain non-magnetic low-spin [LS] Fe2+ (S = 0). The formula is more correctly written as FeFe3Si2Sn7O16 to differentiate the one LS-Fe2+ per formula unit in the intermetallic layer from the three HS-Fe2+ per formula unit in the kagomé oxide layer.

Fe4Si2Sn7O16 also has a unique magnetic ground state below a Néel ordering temperature TN = 3.5 K, in which the spins on 2/3 of the Fe2+ sites in the kagomé oxide layers order antiferromagnetically, while 1/3 remain disordered and fluctuating down to at least 0.1 K. [3] In this talk I will discuss the nature and origins of this “striped” partial spin-liquid state, which has not been observed experimentally nor explicitly predicted theoretically to the best of our knowledge, and possible ways in which its chemistry and physics could be extended.

References
[1] Söhnel, T., et al., Z. Anorg. und Allg. Chemie 624, 708–714 (1998).
[2] Allison, M.C., et al., Dalton Trans. 45, 9689–9694 (2016).
[3] Ling, C.D., et al., Phys. Rev. B 9, 180410 (2017).

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