Calculated magnetic exchange interactions in brownmillerite Ca2Fe2O5

Brownmillerite Ca2Fe2O5 has gained great interest due to its novel properties and wide range of applications. Here, we present a systematically study of the electronic and magnetic properties of Ca2Fe2O5 with first-principles calculations. Our calculation results indicate that the valences of both octahedral Fe and tetrahedral Fe are +3. Using the first-principle linear response (FPLR) method, we calculate the magnetic exchange interactions J's. J's are short-range and negligible for the Fe-Fe atomic pair longer than 6 Å. Three relatively large exchange interactions determine that the magnetic ground state is G-type antiferromagnetism, which is consistent with the experimental results. The magnetic transition temperature calculated with our J's is in agreement with the experiment. Based on the obtained magnetic exchange parameters, we calculate the spin-wave dispersion. We also use the FPLR method to calculate the Dzyaloshinskii-Moriya interactions.