Comparative study of Sr $$_{2}\text {Fe}_{3}\text {Ch}_{2}\text {O}_{3}$$ 2 Fe 3 Ch 2 O 3 (Ch=S, Se): 2-D AFM spin S = 2 ladder systems

We present a microscopic study of the electronic and magnetic properties of the spin ladder systems Sr $$_{2}$$ 2 Fe $$_{3}$$ 3 Ch $$_{2}$$ 2 O $$_{3}$$ 3 (Ch=S, Se) based on density functional calculations and on ab initio-derived effective models. We discuss explicitly the nature of the exchange paths and provide quantitative estimates of magnetic exchange couplings. Although both compounds have similar crystal structures, the values of magnetic exchange interactions are slightly greater for S compound than Se compound. A microscopic modelling based on analysis of the electronic structure of these systems put Sr $$_{2}$$ 2 Fe $$_{3}$$ 3 Ch $$_{2}$$ 2 O $$_{3}$$ 3 (Ch=S, Se) in the interesting class of 2-D AFM spin, S = 2 ladder systems.