Magnetic behavior in metal-free radical thin films

Magnetism in organic materials is very intriguing: the realization of long-range magnetic order in completely metal-free systems combines magnetic moments with useful properties of organic materials. An essential step for applications is the knowledge of the magnetic behavior that, so far, was investigated only in the proximity of light atoms to heavy metals, impurities, or vacancies, and not as an intrinsic property of thin films that are purely organic. Here, we unravel X-ray magnetic circular dichroism at the carbon and nitrogen K-edges in purely organic radical thin films. Our results show that, controlling the preparation, the magnetic behavior is different than in single crystals. Atomistic simulations indicate that the reason for this is the molecular arrangement in the films when compared with that in the single crystal. The tuning of the film magnetic properties by the molecular arrangement is an exciting perspective toward revealing new properties and applications.