NEUTRON-DIFFRACTION STUDY OF CUFEO2

Neutron diffraction study revealed that a powdered CuFeO2, a quasi-two-dimensional antiferromagnet on a triangular lattice (AFT), has two successive magnetic phase transitions at low temperatures. In the high-temperature phase below T(N1) = 16 K, it has a monoclinic magnetic unit cell with five spins in a layer (square-root 7 a x square-root 7 a x 2c, gamma = 141.78-degrees). At T(N2) = 10 K, it shows a discontinuous transition and enters the low-temperature phase with an orthorhombic magnetic unit cell with four spins in a layer (square-root 3 a x 2a x 2c). In both magnetic structures, spins are collinear and parallel to the c axis.