Synthesis, structure and geometrically frustrated magnetism of the layered oxide-stannide compounds Fe(Fe_3−xMn_x)Si₂Sn₇O₁₆

Abstract

Fe4Si2Sn7O16 has a unique crystal structure that contains alternating layers of Fe(2+) ions octahedrally coordinated by O (oxide layer) and Sn (stannide layer), bridged by SiO4 tetrahedra. The formula can be written as FeFe3Si2Sn7O16 to emphasise the distinction between the layers. Here, we report the changes in structure and properties as iron is selectively replaced by manganese in the oxide layer. Solid-state synthesis was used to produce polycrystalline samples of Fe(Fe3-xMnx)Si2Sn7O16 for x≤ 2.55, the structures of which were characterised using high-resolution synchrotron X-ray and neutron powder diffraction. Single-crystal samples were also grown at x = 0.35, 0.95, 2.60 and characterised by single crystal X-ray diffraction. We show that manganese is doped exclusively into the oxide layer, and that this layer contains exclusively magnetically active high-spin M(2+) transition metal cations; while the stannide layer only accommodates non-magnetic low-spin Fe(2+). All samples show clear evidence of geometrically frustrated magnetism, which we associate with the fact that the topology of the high-spin M(2+) ions in the oxide layer describes a perfect kagomé lattice. Despite this frustration, the x = 0 and x = 2.55 samples undergo long-range antiferromagnetic ordering transitions at 3.0 K and 2.5 K, respectively.

Striped magnetic ground state of the kagome lattice in Fe4Si2Sn7O16

“…Fe 1.45 Mn 2.55 Si 2 Sn 7 O 16 at T N = 2.5 K. [12] There was no evidence of spin-glass behavior or a ferromagnetic (FM) component to the ground state. Given their perfectly hexagonal lattices above T N , the ordered magnetic ground state was expected to be either the conventional q = 0 or ( √ 3 × √ 3) solution, which preserve hexagonal symmetry.…”

“…Rietveld-refinements of the nuclear structure above T N were consistent with our previous work using single-crystal X-ray diffraction [11] and a combination of synchrotron X-ray and neutron powder diffraction. [12] New low-angle Bragg peaks emerge for Fe 4 Si 2 Sn 7 O 16 at 1.6 K, below T N , indicative of 3D long-range ordered magnetism (Fig. 2).…”

“…[12] . Rietveld-refinements of the nuclear structure above T N were consistent with our previous work using single-crystal X-ray diffraction [11] and a combination of synchrotron X-ray and neutron powder diffraction.…”

The Effect of Milling Time on the Microstructural Characteristics and Strengthening Mechanisms of NiMo-SiC Alloys Prepared via Powder Metallurgy

“…Data were obtained using neutrons of wavelength λ = 1.622 Å over a range of 39° to 156° [12]. The Electron Back-Scatter Diffraction (EBSD, Zeiss Auriga 60, 20 kV) and Transmission Electron Microscopy (TEM, JEM-2200FS, 200 kV) were employed to identify minor phases as well as their crystal structure, size, distribution, and interaction with the dislocation sub-structure.…”

Striped Magnetic Ground State of the Kagome Lattice in Fe4Si2Sn7O16

“…A triangular lattice of low-spin (LS) Fe 2+ (3d 6 , S = 0) on the 1a Wyckoff site in the stannide layer is magnetically inactive. Fe 1.45 Mn 2.55 Si 2 Sn 7 O 16 at T N = 2.5 K. [12] There was no evidence of spin-glass behavior or a ferromagnetic (FM) component to the ground state. Given their perfectly hexagonal lattices above T N , the ordered magnetic ground state was expected to be either the conventional q = 0 or ( √ 3 × √ 3) solution, which preserve hexagonal symmetry.…”