Photoinduced magnetism in chemical vapor deposited V(TCNE)$_{x}$, $x\sim2$ films

We previously reported[1] that Mn(TCNE)$_{x}$, $x\sim2$, exhibits strong photo-induced magnetism. Here, we extend our study of photo-induced magnetism to V(TCNE)$_{x}$, $x\sim2$ which is a magnetic semiconductor with $T_{C}$ $>$ 350 K, can be grown as a film by a CVD process[2] and can be incorporated in spinvalve system[3]. We report that the excitation of (TCNE) $\pi$ $\rightarrow$ $\pi_{\ast}$ band with blue light (457.9nm) at low temperature(5 K) and low magnetic field(10 Oe) leads to reduction in the magnetization. The photo-excited effects are more substantial at low magnetic field but the saturated magnetization remains the same as that of the ground state. The photo-excited metastable state has a lifetime $>$ 10$^{6}$ s at low temperatures. Only after warming above $\sim$ 100 K does the system completely relax to the state before illumination. Possible origins of the observed effects will be discussed. $^{\ast}$Supported in part by AFOSR Grant No. F49620-03-1-0175 and DOE Grant No. DE-FG02-01ER45931. [1] D. A. Pejakovic $\it{et}$. $\it{al}$., Phys. Rev. Lett. $\bf {88}$, 057202 (2002) [2] K. I. Pokhodnya $\it{et}$. $\it{al}$., Adv. Mater. $\bf{12} $, 410 (2000) [3] J. Bergeson $\it{et}$. $\it{al}$., this Bulletin.