Magnetic short-range order in iron above Tc? Statistical mechanics with many-atom interactions Kamaljeet S. Chana John Samson M.U. Luchini V. Heine 2134/2231 https://repository.lboro.ac.uk/articles/journal_contribution/Magnetic_short-range_order_in_iron_above_Tc_Statistical_mechanics_with_many-atom_interactions/9408506 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. 2006-06-29 10:47:48 band and itinerant models ferromagnetism of Fe and its alloys Physical Sciences not elsewhere classified Condensed Matter Physics