Magnetic Orders and Electronic Structures of Compressive- and Tensile-Strained KCa₂Fe₄As₄F₂ Films

High-T_c ACa₂Fe₄As₄F₂ (A = K, Rb, and Cs) as novel 12442-type Fe-based superconductor has simulated great interests. The magnetic orders of Fe-based superconductor have been widely analyzed since its superconductivity competes with magnetism. The ground state of KCa₂Fe₄As₄F₂ bulk revealed by the first-principle calculation is stripe-type antiferromagnetic (AFM). However, no research on strained KCa₂Fe₄As₄F₂ films has been reported so far. Here, the compressive and tensile strain effects on the ground magnetic orders and electronic structures of KCa₂Fe₄As₄F₂ film (grown on LaAlO₃ and SrTiO₃ substrates, respectively) are discussed based on the first-principle calculations. The stripe-type AFM is stable responding to the compressive strain. The magnetic order is changed from stripe-type AFM of the bulk to checkerboard AFM of the tensile-strained film. This magnetism transition can be attributed to the change of density-of-states contribution of Fe-3d states.