Thermodynamic and critical properties of an antiferromagnetically stacked triangular Ising antiferromagnet in a field

Abstract

We study a stacked triangular lattice Ising model with both intra-and interplane antiferromagnetic interactions in a field, by Monte Carlo simulation. We find only one phase transition from a paramagnetic to a partially disordered phase, which is of second order and 3D XY universality class. At low temperatures we identify two highly degenerate phases: at smaller (larger) fields the system shows long-range ordering in the stacking direction (within planes) but not in the planes (stacking direction). Nevertheless, crossovers to these phases do not have a character of conventional phase transitions but rather linear-chain-like excitations.

Absence of long-range order in a general spin-S kagome lattice Ising antiferromagnet

“…At very low temperatures one can observe an interesting "freezing" phenomenon, similar to the one reported for the SIATL model [10,26,27]. Such a freezing occurs when the chains along the z axis are almost perfectly ferromagnetically ordered but there are still some domain walls separating pieces of the chains, which are ferromagnetically ordered but with spins pointing in opposite directions.…”

“…For example, the increased magnitude of the spin S in the 2D IATL model was found to lead to a so-called partial-disordered (PD) structure (M, 0, −M) with two sublattices ordered antiferromagnetically and the third one disordered [4][5][6][7]. Similar ordering was also confirmed in the actively studied 3D stacked IATL (SIATL) model [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] due to additional unfrustrated interactions in the stacking direction along the z axis. In particular, the system has been found to undergo the phase transition from the paramagnetic to the PD phase, which belongs to the 3D XY universality class [8,12,15,16,22], albeit the tricritical behavior has also been suggested [9].…”

“…Some studies suggested another phase transition occurring at lower temperatures a to a ferrimagnetic phase (M, −M/2, −M/2), with one sublattice fully ordered and two partially disordered [10,12,21]. On the other hand, several other studies argued that due to linear-chain-like excitations in the system there is a crossover to the low-temperature phase, which is a 3D analog of the 2D Wannier phase [9,13,14,26,27]. In the IATL to SIATL dimensional crossover study it was found that the PD phase can also develop in the system consisting of a sufficiently large but finite number of the IATL layers stacked along the z axis.…”