Abstract
The magnetic properties of two samples of acmite, one natural and the other synthetic, were determined using magnetization and susceptibility measurements, Mössbauer spectroscopy and neutron diffraction. Exchange interactions are quite strongly antiferromagnetic, the paramagnetic Curie temperature being -46 K for a purely ferric synthetic sample, but its Néel temperature is only 8 K. The principal magnetic mode has the periodicity of the crystallographic structure and is made of ferromagnetic chains, coupled antiferromagnetically. Moments are oriented in a direction close to the chain axis, c. The antiferromagnetic exchange between adjacent Fe3+ ions in the same chain is overcome by their coupling to a common Fe3+ neighbour in the next chain. This indicates that the whole (SiO4) group can act as a superexchange ligand in silicates.
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1948–1988
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Ballet, O., Coey, J.M.D., Fillion, G. et al. Magnetic order in acmite; NaFeSi2O6 . Phys Chem Minerals 16, 672–677 (1989). https://doi.org/10.1007/BF00223316
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DOI: https://doi.org/10.1007/BF00223316