Phase transitions in classical biquadratic Heisenberg model for strained iron pnictides

Abstract

Based on the notion of magnetically driven nematicity, we study the phase transitions in a frustrated classical Heisenberg model with biquadratic and anisotropic exchange interactions on square lattice by means of Monte Carlo simulations, in order to understand the uniaxial strain effect in BaFe2As2. The variation of both structural and antiferromagnetic transition temperatures with uniaxial stress reported in experiments can be qualitatively reproduced by including the exchange anisotropy, suggesting that the anisotropy may be responsible for the strain effect on the phase transitions.