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Magnetic short-range order in iron above Tc? Statistical mechanics with many-atom interactions

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posted on 29.06.2006, 10:47 authored by Kamaljeet S. Chana, John SamsonJohn Samson, M.U. Luchini, V. Heine
An effective spin Hamiltonian for iron has been derived previously from electronic structure calculations; there are strong many-atom interactions. The exchange interactions Jij depend on the surrounding magnetic order. We investigate the magnetisation and spin correlation function in iron on this basis in two ways: by fitting the Jij to an analytically soluble Hamiltonian (an extended spherical model) and by Monte Carlo simulation. Short-range manyatom interactions do not lead to substantial short range order in the paramagnetic state; the behaviour closely resembles that of the nearest-neighbour Heisenberg model. The main effect is a slight distortion of the magnetisation curve below TC. Longer range oscillatory pair interactions are needed for short-range order, but are not supported by the electronic structure data. We conclude that calculations of the electronic energy in static configurations do not lead to unusual short range order.



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CHANA et al, 1991. Magnetic short-range order in iron above Tc? Statistical mechanics with many-atom interactions. Journal of Physics: Condensed Matter, 3(33), pp. 6455-6471


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This article was published in the journal, Journal of Physics: Condensed Matter [© Institute of Physics] and is also available at: http://www.iop.org/EJ/journal/JPhysCM.