Topochemical synthesis of cation ordered double perovskite oxynitrides.

Topochemical nitridation in ammonia at moderate temperatures of cation ordered SrFeWO produces new antiferromagnetic double perovskite oxynitrides SrFeWON with 0 < x ≤ 1. Nitrogen introduction induces the oxidation of Fe to Fe and decreases T from 38 K (x = 0) to 13 K for SrFeWON which represents the first example of a double perovskite oxynitride with both high cationic order and nitrogen content. This synthetic approach can be extended to other cation combinations expanding the possibility of new materials in the large group of double perovskites.