Recent studies have shown promising results regarding the power conversion efficiency, band-gap tunability, and interfacial charge carrier ability of organic lead halide perovskites. In light of these fundamental abilities, we fabricated a heterostructure: MAPbBr 3 spin-coated on an FePd alloy layer, consisting of both magnetic and optical capabilities. The perovskite’s discrete coverage across the FePd underlayer was confirmed by atomic force microscope, as made up of separate disc-like nanostructures that stand at ∼ 400 nm in height and a size width of up to ∼ 2 µm. We studied the thermal endurance and the inter-facial diffusion stability between MAPbBr 3 and FePd alloy by post-annealing it to temperatures ranging 100–170 ∘ C. The instable interfacial effects of perovskite/FePd was observed at 120 ∘ C, as indicated by the drastic reduction in magnetic coercivity of FePd and the photoluminescence of MAPbBr 3 . This interfacial diffusion behavior between perovskite and FePd advances as the post-annealing temperature reaches 170 ∘ C, supported by the enhanced noise to Kerr signal ratio.