CoFeO (CFO) nanoparticles (NPs) were synthesized by co-precipitation technique and annealed up to 1273K under air and vacuum atmospheres. X-ray diffraction (XRD) analysis of pristine, vacuum and air - annealed samples confirms the spinel structure without any secondary phases. Transmission electron microscopy (TEM) of pristine CFO NPs confirms a wider distribution with an average particle size of 26 ± 7 nm. Further, the estimated activation energy for the growth of CFO NPs under vacuum and air atmosphere is 14.5 kJ/mol and 20.4 kJ/mol respectively. A relative decrease in activation energy for the vacuum - annealed samples suggest part of the thermal energy is utilized for cation migration between the interstitial sites of the spinel structure. Further, the cation migration is unambiguously confirmed by Raman spectroscopy. This study further reveals that the improved saturation magnetization upon vacuum annealing (from 47 emu/g to 80 emu/g) compared to air annealing (76 emu/g) is mainly due to the cation migration and the creation of oxygen vacancies.

Extraordinary optoconductance (EOC) devices with symmetric leads have been shown to have a symmetric positional dependence when exposed to focused illumination. While advantageous for a position sensitive detector (PSD), this symmetric positional dependence, when the device is uniformly illuminated, leads to a minimization of the output voltage. Here, with the aid of a previously employed point charge model, we address two ways to break the symmetry and recover the output signal. The first is to impose uniform illumination but only on half the sample. This method has practical limitations as the device is miniaturized to the nanoscale. The second is via asymmetric placement of the voltage probes in a four-probe measurement. Crucial to the discussion is the effect of the surface charge density. Several ways of modeling the induced surface charge density are presented. Utilizing the above described approach, optimal asymmetric lead positions are found.