Magnetic order in four-layered Aurivillus phases

We determine the viability of four-layered Aurivillius phases to exhibit long-range magnetic order above room temperature. We use Monte Carlo simulations to calculate transition temperatures for an effective Heisenberg model containing a minimal set of required couplings. The magnitude of the corresponding coupling constants has been determined previously from electronic structure calculations for Bi₅FeTi₃O₁₅, for which we obtain a transition temperature far below room temperature. We analyze the role of further neighbor interactions within our Heisenberg model, in particular that of the second-nearest-neighbor coupling within the perovskitelike layers of the Aurivillius structure, as well as that of the weak interlayer coupling, in order to identify the main bottleneck for achieving higher magnetic transition temperatures. Based on our findings, we show that the most promising strategy to obtain magnetic order at higher temperatures is to increase the concentration of magnetic cations within the perovskitelike layers, and we propose candidate compounds where magnetic order could be achieved above room temperature.