Vera Smolyaninova

Doped rare-earth manganese oxides (manganites) exhibit a wide variety of physical phenomena due to complex interplay of electronic, magnetic, orbital, and structural degrees of freedom and their sensitivity to external fields. A photoinduced insulator to conductor transition in charge-ordered (CO) manganites is especially interesting from the point of view of creating photonic devices. We have found a considerable increase (up to 50%) of the photoinduced resistivity changes (Fig. 1a) in the
Bi_0.4Ca_0.6MnO₃ thin film after covering the surface of the film with gold nanoparticles (colloidal gold) (Fig. 1b). This increase can be explained by enhancement of local electromagnetic (EM) field in the vicinity of the gold nanoparticle due to the plasmon resonance. Moreover, the lifetime of the photoinduced changes increases significantly after deposition of the gold nanoparticles on the surface of the film (Fig. 2a). From our previous studies we have found that the magnitude and the lifetime of photoinduced resistivity changes increases, when intensity illumination increases, which is probably due to the increase of the volume of conducting phase, created by light. Therefore, enhanced EM field in the vicinity of gold particles promotes a formation of larger volume of conducting phase (Fig. 2b). This work is supported by NSF Grant DMR-0348939. These results are published in Applied Physics Letters (V. N. Smolyaninova et al., APL 90, 222501)