Neutron powder diffraction experiments on the layered triangular-lattice antiferromagnets RbFe(MoO4)2 and CsFe(SO4)2

Powder specimens of the layered triangular-lattice antiferromagnets RbFe(MoO4)2 and CsFe(SO4)2 were prepared and neutron powder diffraction experiments were carried out in order to determine the magnetic structure. The magnetic structure of both compounds is the so-called image structure in the triangular plane and is incommensurate between the planes. The ordered moments are confined in the basal ab-plane. It is also found that RbFe(MoO4)2 exhibits structural phase transition at around 190 K from image to image.