Multiple Photonic Responses in Organic Magnetic Semiconductor V(TCNE)x(x ~ 2)

Summary form only as given. The V(TCNE)X (x - 2)is a fully spin-polarized semiconductor, whose magnetic ordering temperature exceeds room temperature (T, > 350 K), and electronic transport is a thermally activated mechanism involving the Coulomb energy split z band. The spin polarized valence and conduction bands are of importance for spintronics applications. Substantial decrease of magnetization by illuminating with light (X = 457.9 nm) into the g -e> transition for (TCNE) has been found at low temperature (T < 100 K). The photo-excited metastable state has a lifetime > 107s at low temperatures and completely relaxes to the state present before illumination after annealing up to 250 K. Analysis of the photoinduced ESR indicates strong increase of magnetic anisotropy by the light irradiation. We report a multiphotonic response with a substantial increase of conductivity induced by light (X = 457.9 nm). The temperature dependence of resistivity clearly indicates substantial decrease in activation energy for electronic hopping. The photoinduced effects are proposed to originate from structural changes triggered by g - z excitation in (TCNE) molecules, which leads to modulation of the magnetic exchange energy J and the activation energy AE. Photoinduced IR studies support this mechanism for multiphotonic responses. *Supported in part by AFOSR Grant No. F49620-03-1-0175,