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Discovery of an Ideal HgO12 Icosahedron and Magnetodielectric Coupling in HgCu3Ti4O12
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DOI：10.1002/aelm.70450.png)
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Abstract
En 中文
We report the first successful high-pressure synthesis and comprehensive characterization of A-site-ordered quadruple perovskite HgCu3Ti4O12. The compound crystallizes in the cubic Im-3 structure with Hg2+Cu2+3Ti4+4O2−12 valence configuration. A remarkable structural feature is the observation of a perfectly regular and undistorted HgO12 icosahedron, representing the highest and most symmetric oxygen coordination environment reported for Hg2+ in any oxide material. Magnetic and specific heat measurements reveal the antiferromagnetic ordering at TN = 31 K, driven by indirect super-exchange interaction via the Cu2+-O2−-Ti4+-O2−-Cu2+ pathway. The dielectric properties of HgCu3Ti4O12 display a significantly lower, more intrinsic permittivity (∼102) with two distinct Debye-type relaxation processes: a high-temperature process related to oxygen vacancy–defect dipole reorientation, and a low-temperature process attributed to low-energy local lattice vibrations of the TiO6 or CuO4 units. Crucially, a dielectric anomaly around TN suggests the presence of magnetodielectric coupling, likely mediated by the aforementioned indirect super-exchange interaction pathway. This work elucidates the structure–property relationships in HgCu3Ti4O12, highlights the critical role of cation chemistry in tailoring functional properties, and demonstrates the potential of A-site-ordered quadruple perovskites as a versatile platform for exploring coupled electronic, magnetic, and dielectric phenomena.
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