Design of a novel magnet exhibiting photoinduced magnetic pole inversion based on molecular field theory

We show a novel magnetic phenomenon, "photoinduced magnetic pole inversion", which occurs even in the absence of an external magnetic field. The key of this strategy is to control the compensation temperature by a pure photoprocess. Here, we combined two magnetic behaviors which were developed recently. One of them is the photoinduced change of magnetization for some of the Prussian blue analogues. The other is a so-called mixed ferro-ferrimagnetism in the system of ternary metal Prussian blue analogues. We show a strategy to obtain this phenomenon based on molecular field (MF) theory and we design new classes of ternary metal Prussian blue analogues, ((FexMn1-xII)-Mn-II)(1.5)[Cr-III(CN)(6)]. zH(2)O, including photosensitive Fe-II-Cr-III sites. Their magnetic properties, such as saturation magnetization, coercive field, Curie temperature, and compensation temperature, were controlled by changing the compositional factor x. When the material for x = 0.40 was irradiated by visible Light under a weak external magnetic field (10 G), the photoinduced magnetization reversal occurred. This phenomenon can be simulated well by the MF theory considering only two types of superexchange couplings between the nearest neighbor sites, one for Fe-II-Cr-III and the other for Mn-II-Cr-III.