  Molecular systems are materials that intersect with many different promising
fields such as organic/molecular electronics and spintronics, organic magnetism
and quantum computing1-7. Particularly, magnetism in organic materials is very
intriguing: the possibility to realize long-range magnetic order in completely
metal-free systems means that magnetic moments are coupled to useful properties
of organic materials, such as optical transparency, low-cost fabrication, and
flexible chemical design. Magnetic ordering in light elements, such as nitrogen
and carbon, has been studied in magnetic-edged graphene nanoribbons8 and
bilayers9, and polymers10 while in organic thin films most of the
investigations show this effect as due to the proximity of light atoms to heavy
metals, impurities, or vacancies11. Purely organic radicals are molecules that
carry one unpaired electron giving rise to a permanent magnetic moment, in the
complete absence of metal ions.12-14 Inspired by their tremendous potential,
here we investigate thin films of an exceptionally chemically stable Blatter
radical derivative15 by using X-ray magnetic circular dichroism (XMCD)16-18.
Here we observe XMCD at the nitrogen K-edge. Our results show a magnetic
ordering different than in the single crystals and calculations indicate,
although weak, a long-range intermolecular coupling. We anticipate our work to
be a starting point for investigating and modelling magnetic behaviour in
purely organic thin films. The tuning of the magnetic properties by the
molecular arrangement in organic films is an exciting perspective towards
revealing new properties and applications.
