Institute of Quantum Materials Science, IQMS

Intrinsic nanoscale inhomogeneity in ordering systems due to elastic-mediated interactions

I. K. Razumov, Yu. N. Gornostyrev and M. I. Katsnelson

EPL, 80, 66001 (2007)

Phase diagram and pattern formation in a two-dimensional Ising model with coupling between order parameter and lattice vibrations are investigated by Monte Carlo simulations. It is shown that if the coupling is strong enough (or phonons are soft enough) a short-range order exists in the disordered phase for a broader temperature interval. Different types of this short-range order (stripe-like, chessboard-like, etc.) depending on the temperature and model parameters are investigated. With further increase of the coupling, a reconstruction of the ground state happens and new ordered phases appear at low enough temperatures.

Formulas: Model

We take into account energy of deformation of crystal lattice in harmonic approximation and Heisenberg magnetic contributio

with exchange interaction energy which is depend on distance

Distribution of atomic displacements ux + uy for the FM case at T = 1 without spin lattice coupling domains (a) and at T = 3.5 with the spin-lattice coupling pattern (b). The results are presented for 103 flips per spin.

A phase diagram for the ferromagnetic case. 1, 2, and 3 labels the ferromagnetic phase, chessboard ordering, and disordered (paramagnetic) phase, respectively.