The crystal and magnetic structural studies of metal halide double perovskites Cs2(Ag:Na)FeCl6 by neutron powder diffraction

Magnetic halide perovskites have emerged as potential materials for magnetic functionalized semiconductors. However, stable optoelectronic halide perovskites with long-range magnetic ordering remain scarce. Here we propose to study the magnetic ordering in the emerging stable and non-toxic Cs2(Na:Ag)FeCl6 double perovskites by powder neutron diffraction. Our pilot study by x-ray diffraction, superconducting quantum interference devices, and electron paramagnetic resonance proved a long-range antiferromagnetic order, with strong magnetic frustration. The magnetic frustration factor increases in (Ag:Na) alloy samples. The possible scenario is that Cs2AgFeCl6 and Cs2NaFeCl6 have different magnetic ground states. The alloy between those two would lead to a configuration disorder that further destabilizes the AFM phase. Therefore, determining the magnetic ground state in Cs2(Ag:Na)FeCl6 alloys is vital to answer the origin of the magnetic behavior. In addition, the refined magnetic structure from the experiment will be an experimental basis for the theoretical prediction of magnetic and optoelectronic properties of metal halide double perovskites. The proposed study on Cs2(Ag:Na)FeCl6 would serve as a model system for the emerging field of magnetic halide double perovskites.