Optical tunability of magnetoimpedance properties in La${}_{0.7}$Sr${}_{0.3}$MnO${}_3$-Glass nanocomposites: a signature of Opto-spintronics

We have investigated glass content ratio dependent magneto-optical tunability of complex impedance spectroscopy study in La${}_{0.7}$Sr${}_{0.3}$MnO${}_3$ (LSMO)-Glass nanocomposites prepared through chemical pyrophoric reaction process. Interestingly, our experimental results provide evidence of optical tunability of magnetoimpedance (MI% = $\frac{Z(H,f)-Z(0,f)}{Z(0,f)}$ × 100) in these nanocomposites. Our experimental signature shows that MI increases with increasing weight percent of glass (x%) up to 0.2% glass, but it decreases rapidly with further increasing of x% to 0.5% due to formation of colloidal cluster of LSMO grains. With the rise in applied magnetic field (H), negative magnetoimpedance (MI) of all the nanocomposites is found to be increased significantly. This is because, under applied H, LSMO domain walls may have started to depin from their pinning centres and consequently, realignment of spins occur which increase the magnetic permeability (µ) of the system. Hence, skin depth of the material decreases. Moreover, under optical illumination, nonmonotonic grain boundary (GB) impedance evidencing maximum MI values in S2 sample, attributes glass content percent dependent exciton dissociation and charge separation at interfacial GB region. However, at constant high applied H, with increasing optical illumination magnetic spins may have become decoherent which reduces µ values of all the nanocomposites. As a result, skin depth increases which leads to decrease of MI effect of all the samples. This optical tunability of MI is quite promising for technological implementation in Opto-spintronics devices.