Photoinduced antiferromagnetic to ferromagnetic crossover in organic systems

Magnetization reversal is important for different technological applications. Photoinduced magnetization reversal is easier to implement than conventional reversal methods. Here, we theoretically design and investigate the photomagnetic property of azobenzene based diradical systems, where trans isomers convert into corresponding cis forms upon irradiation with light of appropriate wavelength. The coupling constant values have been estimated using the broken symmetry approach in the density functional theory framework. In each case, the trans isomer is found to be antiferromagnetic, while the cis form is ferromagnetic in nature. Therefore, photoinduced magnetic crossover from antiferromagnetic to ferromagnetic regime would be observed. This is a new observation in case of the systems of organic origin. Importance of such systems for photomagnetic switches, sensors, high density data storage, spin valves, and semiconductor spintronic materials have also been discussed with support from density of state analysis, singly occupied molecular orbital-singly occupied molecular orbital energy gaps and spin density plots.