The structures and magnetic properties of Fe_xCo_1−xSb₂O₄ and Mn_xCo_1−xSb₂O₄, 0 ≤ x ≤ 1

Abstract

MxCo1−xSb2O4 (M = Mn, Fe) shows rotation of magnetic moments within the structure, tuneable with increasing x.

Synthesis and magnetic characterisation of Fe1−xMgxSb2O4 (x = 0.25, 0.50, 0.75) and their oxygen-excess derivatives, Fe1−xMgxSb2O4+y

“…The change in the Weiss constant also reflects the weakening of magnetic exchange as x increases but |y| is always significantly larger than the ordering temperatures. This has previously been observed in related materials 12 and is commonly observed for antiferromagnetic order when the mean field of each magnetic sublattice is not solely determined by the other sublattice. In order to explore the nature of the magnetic order in Fe 1Àx Mg x Sb 2 O 4 , PND data were collected at 300 and 4 K for Fe 0.5 Mg 0.5 Sb 2 O 4 .…”

“…High moments were also reported for some materials containing mixed transition metal ions (Mn/Co and Fe/Co) in this structure and this was attributed to the occurrence of small clusters of cations for which ferromagnetic order was retained above the long-range magnetic ordering temperature. 12 In the present study, C-type order provides ferromagnetic order within each individual chain of octahedra, so small groups of Fe 3+ cations would be expected to experience strong ferromagnetic exchange; the general disorder caused by the substitution of Mg 2+ ions would weaken the antiferromagnetic exchange between the chains so some ferromagnetic clusters could exist to high temperatures and result in the slightly high magnetic moments determined from the susceptibility data for the oxidised samples, Table 6.…”

“…11 We have also prepared new phases that contain mixed magnetic cations on the M site and determined their magnetic properties. 12 Two principal types of antiferromagnetic order are observed for magnetic MSb 2 O 4 compounds: A-type and C-type 13 with the magnetic moments aligned as shown in Fig. 2.…”

“…Low temperature powder neutron diffraction (PND) experiments, for example, revealed that the A-type magnetic ground state found for both FeSb 2 O 4 and MnSb 2 O 4 is gradually converted to C-type with increasing Co 2+ substitution in the series with compositions Fe 1Àx Co x Sb 2 O 4 and Mn 1Àx Co x Sb 2 O 4 . 12 In addition, the A-type order in FeSb 2 O 4 can also be converted to C-type by partial oxidation of Fe 2+ to Fe 3+ which occurs in FeSb 2Àx Pb x O 4 . 11 Of particular interest is the ferromagnetic ground state observed below B7.4 K in the isostructural CuAs 2 O 4 , 14 where both intrachain and interchain magnetic exchange interactions are ferromagnetic.…”

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“…We have also prepared new phases involving substitution on the M site. The magnetic moments deduced from neutron diffraction and magnetic susceptibility measurements in the series of composition Fe 1−x Co x Sb 2 O 4 suggested the existence of some short range correlations within the chains [17] whilst in materials of formulation Fe 1−x Mg x Sb 2 O 4 , the decrease in magnetic ordering temperature with increasing concentrations of magnesium was associated with non-magnetic Mg 2+ ions weakening the magnetic interactions between Fe 2+ ions [18]. An interesting feature of these materials has been the demonstration of their capacity to accommodate additional oxygen within their structures [19].…”