The $\mathrm{V}(\mathrm{TCNE}{)}_x$, $x\sim 2$ is an organic-based amorphous ferrimagnet, whose magnetic behavior is significantly affected in the low field regime by the random magnetic anisotropy. It was determined that this material has thermally reversible persistent change in both magnetization and conductivity driven by the optical excitation. Here, we report results of a ferrimagnetic resonance study of the photoinduced magnetism in $\mathrm{V}(\mathrm{TCNE}{)}_x$ film. Upon optical excitation ($\lambda \sim 457.9\mathrm{nm}$), the ferrimagnetic resonance spectra display substantial changes in their linewidths and line shifts, which reflect a substantial increase in the random magnetic anistropy. The results reflect the role of magnetic anisotropy in disordered magnets and suggest a novel mechanism of photoinduced magnetism in $\mathrm{V}(\mathrm{TCNE}{)}_x$ induced by the increased structural disorder in the system.

• Received 14 April 2007

DOI:https://doi.org/10.1103/PhysRevLett.99.157205