High frequency (240 GHz) ferrimagnetic resonance (FMR) of room temperature organic based magnetic semiconductor V[TCNE]$_{x}$ (x$\sim $2) films

V[TCNE]$_{x}$ (x$\sim $2) is an organic based ferrimagnetic semiconducting material ($\rho _{300K}\sim $10$^{2}\Omega $.cm and activation energy, E$_{a} \quad \approx $ 0.5 eV) with an ordering temperature well above room temperature. Magnetoresistance (MR) behavior of this material has been explained on the basis of spin polarization of charge carriers in the $\pi $* electronic subbands of [TCNE]$^{-}$ forming a `half-semiconductor'.[1,2] X-band ($\sim $9 GHz) ferrimagnetic resonance (FMR) studies on V[TCNE]$_{x}$ (x$\sim $2) have been reported earlier.[3] Temperature and angular dependence of FMR spectra of V[TCNE]$_{x}$ (x$\sim $2) films, obtained using $\sim $240 GHz radiation, indicate the coexistence of long-range magnetic ordering and glassy behaviors. These results will be discussed in terms of competing interactions between V$^{2+}$ and [TCNE]$^{-}$ spins based on the local structural order. 1.V.N. Prigodin et. al., Adv. Mater. \textbf{14}, 1230 (2002). 2.N.P. Raju et. al., J. Appl. Phys., \textbf{93}, 6799 (2003). 3.R. Plachy et. al., Phys. Rev. B \textbf{70}, 064411 (2004).