Magneto-optical tunability of impedance through electronic structure modification in ZnO–rGO/LSMO/ITO spintronic devices

Abstract

In this paper, we have investigated red light (∼660 nm) and magnetic field dependence of impedance across (100−x)% ZnO(zinc oxide)–x% rGO(reduced graphene oxide)/La0.7Sr0.3MnO3(LSMO)/ITO (x=0,0.6,0.8,100) heterostructure devices. Field-induced scattering due to the spin filter effect and spin polarized tunneling (SPT) have been extracted from the zinc oxide–reduced graphene oxide nanocomposite/LSMO space charge region (ZnO–rGO/LSMO SCR) and the LSMO active region of the devices, respectively. Higher SPT leads to higher LSMO SCR scattering across the devices. Devices with higher rGO contents could not be fitted with two RC circuits as resistance values because the two phenomena are incomparable with each other. Light-induced scattering has been observed at the ZnO–rGO nanocomposite active region and ZnO–rGO/LSMO SCR of the devices. For composite devices with x=0.8 and 0.6, higher photocarrier generation at ZnO–rGO nanocomposite active layer leads to enhanced scattering at LSMO SCR with light illumination. Light-dependent scattering at both regions, however, follows almost same decreasing trend for bare devices with x=0, 100. The decreasing trend of light-dependent scattering for ZnO/LSMO/ITO and rGO/LSMO/ITO bare devices suddenly gets reversed and, eventually, follows an increasing trend at magnetic field ambiance of 0.5 and 1 kOe, respectively. The LSMO SCRs of the bare devices got enhanced with the field, leading to a light-dependent response similar to composite devices at the higher field.