Control of the Electrical Properties in Spinel Oxides by Manipulating the Cation Disorder

In this work, the impact of cation disorder on the electrical properties of biaxially textured Co 2 ZnO 4 and Co 2 NiO 4 thin films grown by pulsed laser deposition are investigated using a combination of experiment and theory. Resonant elastic X‐ray diffraction along with conductivity measurements both before and after post‐deposition annealing show that Co 2 ZnO 4 and Co 2 NiO 4 exhibit opposite changes of the conductivity with cation disorder, which can be traced back to their different ground‐state atomic structures, being normal and inverse spinel, respectively. Electronic structure calculations identify a self‐doping mechanism as the origin of conductivity. A novel thermodynamic model describes the non‐equilibrium cation disorder in terms of an effective temperature. This work offers a way of controlling the conductivity in spinels in a quantitative manner by controlling the cation disorder and a new design principle whereby non‐equilibrium growth can be used to create beneficial disorder.