CSLH91.pdf (977.31 kB)
Download fileMagnetic short-range order in iron above Tc? Statistical mechanics with many-atom interactions
journal contribution
posted on 29.06.2006, 10:47 authored by Kamaljeet S. Chana, John SamsonJohn Samson, M.U. Luchini, V. HeineAn 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.
History
School
- Science
Department
- Physics