Crossover from first- to second-order transition in frustrated Ising antiferromagnetic films

Abstract

In the bulk state, the Ising face-centered-cubic (fcc) antiferromagnet is fully frustrated and is known to have a very strong first-order transition. In this paper, we study the nature of this phase transition in the case of a thin film as a function of the film thickness. Using Monte Carlo simulations, we show that the transition remains first order down to a thickness of four fcc cells (eight atomic layers). It becomes clearly second order at a thickness of two fcc cells, i.e., four atomic layers. It is also interesting to note that the presence of the surface reduces the ground-state degeneracy found in the bulk. For the two-cell thickness, the surface magnetization is larger than the interior one. It undergoes a second-order phase transition at a temperature TC while interior spins become disordered at a lower temperature TD. This loss of order is characterized by a peak of the interior spins susceptibility and a peak of the specific heat which do not depend on the lattice size suggesting that either it is not a real transition or it is a Kosterlitz-Thouless nature. The surface transition, on the other hand, is shown to be of second order with critical exponents deviated from those of pure two-dimensional Ising universality class. We also show results obtained from the Green's function method. A discussion is given.

Spin resistivity in frustrated antiferromagnets

“…1. 34 For |J s | < 0.5|J |, the ground state is composed of ferromagnetic xy planes antiferromagnetically stacked in the z direction as shown in the upper figure of of up-and down-spin planes in the y direction while the lower figure is an alternate stacking of up-and down-spin planes in the x direction. These degenerate states are not equivalent in the spin transport in the x direction as seen below: in the first degenerate state, the itinerant spins move in the x direction between an up-spin plane and a down-spin plane, while in the second degenerate state the itinerant spins meet successively an up-spin plane and a down-spin plane perpendicular to their trajectories.…”

“…This system is known to be fully frustrated with a strong first-order transition in the Ising case. 33, 34 The spin resistivity is known to be very sensitive to the nature of the ordering of the media through which the itinerant spins move: local disordering (for instance, disordering near film surfaces, around magnetic impurities), magnetic instability, and so on. The fcc AF is thus a very good candidate where exotic behaviors are expected for the spin resistivity.…”

Re-orientation transition in molecular thin films: Potts model with dipolar interaction

“…We have now at hand these efficient techniques to deal with complex systems. We can mention our recent investigations by MC techniques on multilayers [29], on frustrated surfaces [30,31] or on surface criticality [32,33].…”

Statistical Physics Approach to Liquid Crystals: Dynamics of Mobile Potts Model Leading to Smectic Phase, Phase Transition by Wang–Landau Method

“…The reader is referred to the original papers [ 34 , 35 ] for details. The efficiency of the Wang–Landau method has been shown in several systems where the nature of the transition has been a controversial subject [ 51 , 52 , 53 , 54 , 55 , 56 ]. We know that a flat energy histogram is obtained when the transition probability to the microscopic state of energy E is .…”