Determination factors of magnetic anisotropy in a layered iron-based pnictide and its related compounds

From magnetic orientation under static and rotating magnetic fields for REOFeAs, REOCuS and FeCh, we discuss determination factors of magnetic anisotropies for the above compounds. Behaviours of the magnetic orientation were quite different between REOFeAs and REOCuS, and revealed that FeAs layers and RE3+ ions played main roles as determination factors of magnetic anisotropies in REOFeAs and REOCuS, respectively. Furthermore, FeSe and FeTe compounds with the same crystal structure possess different magnetic axes, and we clarified that FeTe was the one and only compound with the easy axis parallel to the c-axis among the Fe- based layered compounds.