Figure 3.

Engineering of SACs with the spin-state tuning strategy. (a) The synthesis process of Fe SACs and spin-state tuning of Fe^III, (b) ⁵⁷Fe Mössbauer spectroscopy with D1 and D2 peaks assigned to medium- and low-spin Fe^III, and (c) 1/χ_m plots.⁹⁰ (d) Crystal structure of spinel ZnCo₂O₄ with Co in octahedral sites, (e) illustration of the Co³⁺ spin state and Co–O–Co spin channel with the rising of the cobalt spin state, (f) the octahedra distortion, (g) temperature-dependent magnetization characterizations of the as-prepared samples at H = 1000 Oe, and (h) the ratio of high and low spin state Co³⁺ calculated based on the effective magnetic moment.⁹² (a-c) Reproduced with permission from ref (90). Copyright 2022 Wiley-VCH. (d-h) Reproduced with permission from ref (92). Copyright 2021 Wiley-VCH.