The varied magnetic polarons and related photoluminescence behaviors of layer PA2CdCl4: Fe(III) structures

Ferromagnetic polaron (FMP) coupling and antiferromagnetic polaron (AMP) coupling have been extensively studied in zero-dimensional and three-dimensional structures. However, studying their electronic structures and photophysical processes in layer structures still faces significant challenges. In this work, we synthesized minor and rich Fe ion-doped PA2CdCl4 layer structures by slow-cooling crystallization and adjusting the Fe ion concentration. In minor Fe ion-doped PA2CdCl4, the Fe–Fe ion pair easily replaces the Cd–Cd pairs in the corner-sharing octahedra layer to form a FMP and promote a red emission (618 nm) from localized exciton-magnetic polarons (LEMPs). In the rich Fe ion doping, AMPs can be easily formed when Fe ions obtain electrons from NH2 and convert into a low-spin state, coexisting with FMPs. The increasing number of AMPs promote the formation of a new Fe-aniline charge-transfer band; the co-work of AMPs and the Fe-aniline charge-transfer band result in a blue emission (466 nm). The result of the magnetic field-dependent photoluminescence (PL) measurement indicates that the population, energy and the spin direction of AMPs and FMPs can have a direct impact on the luminescence behavior of Fe ion-doped PA2CdCl4 layered structures. The density functional theory (DFT) calculation result indicates that Fe–Fe pairs under ferromagnetic (FM) coupling interact via dx2–y2 and dz2 orbitals. Fe–Fe pairs under antiferromagnetic (AFM) coupling on the dxy and dz2 orbitals. This work provides new insights into the varied magnetic polarons of layer structures and their effect on PL behavior.