XY model on a four-layer triangular lattice with competition between ferromagnetic and antiferromagnetic layers

We investigate an XY model on a four-layer triangular lattice with two ferromagnetic layers sandwiched by two antiferromagnetic layers by using Monte Carlo simulations. The chirality on the middle layers with ferromagnetic intralayer interactions shows very steep increase as temperature increases in a temperature range, which is below the chirality transition temperature. A critical exponent is defined for this chirality change and its value is the same as that for a two-layer system and for a three-layer system with competition between ferromagnetic and antiferromagnetic layers.