Modeling random strain by means of a random-field Ising-O(3) model*

Several iron-based superconducting materials feature a structural phase transition as well as a magnetic transition into a low-temperature phase with stripe-like spin-order. We study the relation between the structural and magnetic phase transitions in these materials by means of Monte Carlo simulations, and we analyze the effects of random strain commonly found in the samples.
To do so, the magnetic properties of these materials are modeled via an anisotropic (layered) three-dimensional Ising-0(3) model which describes both spin and nematic (stripe) degrees of freedom. Local random strain acts as a random field term coupling to the nematic variables. We perform large-scale simulations of this model to determine the critical random field strength, above which the nematic order is destroyed by the field, and no phase transition occurs.