Electronic structures of ternary iron arsenides AFe$_2$As$_2$ (A=Ba, Ca, or Sr)

摘要

We have studied the electronic and magnetic structures of the ternary ironarsenides AFe$_2$As$_2$ (A = Ba, Ca, or Sr) using the first-principles densityfunctional theory. The ground states of these compounds are in a collinearantiferromagnetic order, resulting from the interplay between the nearest andthe next-nearest neighbor superexchange antiferromagnetic interactions bridgedby As $4p$ orbitals. The correction from the spin-orbit interaction to the bandstructure is small. The pressure can reduce dramatically the magnetic momentand diminish the collinear antiferromagnetic order. Based on the calculations,we propose that the low energy dynamics of these materials is describedeffectively by a $t-J_H-J_1-J_2$-type model.