We propose that the inability of the m = 5 Aurivillius structure to accommodate Mn⁴⁺ concentrations above 6.6% at the B-site likely drives the structural rearrangement observed, leading to the formation of a higher m-phase, as evidenced by XRD and TEM analysis. This rearrangement, along with an increased number of A-site cations, is posited to enhance the tolerance factor of the perovskite unit (see Supplementary Information, Section SI7), as shown in Table . The structural adaptation to incorporate higher magnetic cation content in the B6TFMO