where A and hν are the proportionality constant and incident photon energy respectively and n is a constant. Here, n value is equal to 1/2 for direct allowed transition from the valence band to the conduction band. The direct band gap energy can be evaluated by extrapolating the linear parts of (αhν) 2 versus hν curve to αhν¼0. As shown in the insert of Fig. 8, the direct band gap values of AZO films are found to be increased from 3.10 to 3.15 eV with increase of external magnetic field from 0 to 6.0 mT respectively. The variation in optical band gap (Eg) indicates here the dependence of Eg on the applied magnetic field. To measure the quality information of the deposited AZO films, the figure of merit (ΦTC) value was calculated using the following expression [25]: ΦTC =− ρ 1/ lnT ( )