Showing papers by "Julia M. Yeomans published in 1983"

Interface properties of the two-dimensional Blume-Emery-Griffiths model

Abstract: The authors study the interface behaviour of the two-dimensional Blume-Emery-Griffiths model (1971) which is described by the Hamiltonian H=-J Sigma (ij)SiSj=K Sigma (ij)Si2Sj 2+D Sigma iSi2 Si=1, 0, -1. An interface is introduced into the system by fixing the spins on opposite boundaries in two different states, +1 and -1. They pay particular attention to the appearance of an excess of the third state, 0, in the vicinity of the interface. The net adsorption of the non-boundary state is studied near critical, first-order and tricritical transitions. Two methods have been used to attack this problem, the Monte Carlo technique and a modified version of the interface free energy approximation of Muller-Hartmann and Zittartz (1977) which is seen to give a surprisingly good description of interface properties in three-state systems.

Tricritical behaviour in a bond-dilute spin model

Abstract: The authors use a Migdal-Kadanoff renormalisation group to study the behaviour of the Blume-Emery-Griffiths model when quenched, random-bond dilution is introduced. Phase diagrams are calculated for varying dilution. The behaviour of the multicritical points of the pure system as dilution is introduced is of particular interest. They find that the tricritical temperature tends to zero as the percolation threshold is approached but that the tricritical field remains finite in agreement with experimental results on the dilute metamagnet FepMg(1-p)Cl2.

Phase diagram of the ANNNI model in a field using a low-temperature series technique

Abstract: The authors study the behaviour of the axial next-nearest-neighbour Ising (ANNNI) model in a field using low-temperature series. The analysis is a generalisation of the inductive scheme introduced by Fisher and Selke (1980, 1981) for the zero-field case. An infinite sequence of commensurate phases of mean wavevectors qj= pi j/(2j+1)a, j=2, 4, 6 ..., is shown to exist in the vicinity of a multiphase line. These phases form a subset of the sequence occurring for zero field. At large fields, the long-wavelength commensurate phases become unstable to the ferromagnetic state and an infinite sequence of triple points is seen.