This study contributes a comprehensive understanding of structural adaptation to compensate for charge and size differences when accommodating higher concentrations of magnetic cations in multiferroic Aurivillius phases. The initial investigation focused on determining the solubility limit for magnetic Fe and Mn cations within the m = 5 Aurivillius phase structure. XRD and TEM analyses of Bi6TixFeyMnzO18 (x = 2.3 to 3.2, y = 1.2 to 2.0, z = 0.3 to 0.9) compositions revealed that when the Ti 4+ content was lowered below 54%, a discernible transformation occurs, leading to the formation of a mixed-phase sample consisting of both the main m = 5 Aurivillius phase and the m = 6 phase. The prevalence of the m = 6 phase within the m = 5 phase matrix increased with decreasing Ti 4+ content. Upon elevating the nominal Mn 4+ content to 14%, the m = 5 structure transforms into a single-phase m = 6 structure, with each perovskite block now containing nominal 4%Mn 4+ . The transition to the higher-layered Aurivillius homologue is interesting, especially considering the thermodynamic constraints on expanding layering periods. It suggests that chemical modifications are pivotal in stabilizing the formation of the m = 6 Aurivillius phase. This transition to the higher m = 6 phase reduces the relative fraction of Mn 4+ required for charge neutrality in the material (refer to Table ). Consequently, the structure becomes more tolerant of higher magnetic cation content. Correspondingly, the average calculated oxidation state for Mn also decreases, falling within the range of values reported previously for stable Aurivillius phase compositions.