Magnetic phase transitions in (1−x)BiFeO3–xPbFe1/2Sb1/2O3 solid solutions studied by the Monte Carlo method

Bismuth ferrite (BiFeO${}_3$, BFO) and its solid solutions are promising multiferroic materials with both magnetic and ferroelectric orderings. One such solid solution is $(1-x)$BiFeO${}_3$ – $x$PbFe${}_{1/2}$Sb${}_{1/2}$O${}_3$. PbFe${}_{1/2}$Sb${}_{1/2}$O₃ (PFS) is also considered multiferroic, exhibiting a high peak in the dielectric constant at 190 K and electric polarization loops below this temperature. However, the magnetic properties and the ground state of PFS remain subjects of debate. The magnetic behaviour is arguably further complicated by its strong tendency to form cation-ordered structures. In this study, we investigate the magnetism in the $(1-x)$BiFeO${}_3$ – $x$PbFe${}_{1/2}$Sb${}_{1/2}$O${}_3$ solid solutions using the Monte Carlo method. The evolution of the magnetic phase transition temperature and of the type of magnetic ordering with varying PFS concentration is examined. We consider different scenarios of Fe$-$Sb atomic ordering: disordered, clustered, or with varying degrees of ordering, and build phase diagrams providing insights into the magnetism of these solid solutions.