The magnetic phase diagram of Sr2Fe3Ch2O3 (Ch = S, Se)

We here report on the complex magnetic structures within the Sr2Fe3 Ch 2 O3 (Ch = S and Se) system that we studied by means of powder neutron diffraction. Successive magnetic transitions occur in the magnetic phase diagram of both compounds with an incommensurate character of the magnetic structure at higher temperatures and a lock-in to commensurate low temperature structures. The commensurate propagation vector for the Ch = S compound is different from the Se containing compound which could be indicative for changes in the size of competing exchange interactions implied by structural changes within the two materials.