Magnetic structure of undistorted hexagonal ferrites, Lu0.2In0.8FeO3

We report on the crystal and magnetic structure of bulk hexagonal (Lu,In)FeO3. Neutron powder diffraction revealed that Lu0.2In0.8FeO3 has a single-phase P6(3)/mmc structure down to T approximate to 3K and shows an antiferromagnetic transition at T-N approximate to 164K. Unlike the distorted hexagonal LuFeO3 family with an A(2)(Gamma(2))-type spin configuration, undistorted hexagonal Lu0.2In0.8FeO3 shows either an A(1)(Gamma(1)) or a B-1(Gamma(3))-type spin configuration below T-N, which does not produce the c-directional canted ferromagnetic moment. A significant reduction in the ordered magnetic moment was observed at 3K without trimerization, and hints of a magnetic cluster state were observed in the paramagnetic phase near room temperature. Therefore, the system presents a rare example to study the geometrically frustrated magnetism in the undistorted hexagonal magnet that has a perfect triangular lattice below room temperature.