Room‐Temperature Magnetic Field Effect on Excitonic Photoluminescence in Perovskite Nanocrystals

Magnetic‐field‐enhanced spin‐polarized electronic/optical properties in semiconductors are crucial for fabricating various spintronic devices. However, this spin polarization is governed by weak spin exchange interactions and easily randomized by thermal fluctuations; therefore, it is only produced at cryogenic temperatures, which severely limits the applications. Herein, a room‐temperature intrinsic magnetic field effect (MFE) on excitonic photoluminescence is achieved in CsPbX3:Mn (X = Cl, Br) perovskite nanocrystals. Through moderate Mn doping, the MFE is enhanced by exciton–Mn interactions, and through partial Br substitution, the MFE is stabilized at room temperature by exciton orbital ordering. The orbital ordering significantly enhances the g‐factor difference between electrons and holes, which is evidenced by a parallel orbit–orbit interaction among excitons generated by circular polarized laser excitation. This study provides a clear avenue for engineering spintronic materials based on orbital interactions in perovskites. A room‐temperature intrinsic magnetic field effect is realized in perovskite nanocrystals. The circular polarization of exciton photoluminescence in CsPbCl3 is enhanced by sp–d interactions with Mn doping, and is further stabilized by exciton orbital ordering with partial Br substitution, which induces 4.6% circular polarization ratio at room temperature in a 35 T magnetic field.