ND4FeBr3, a new one-dimensional S=1 antiferromagnet Conferences uri icon

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abstract

  • Compounds of chemical formula AFeX3 (A=Rb,Cs,Tl, and X=Cl, Br) provide an isomorphous series of one-dimensional induced-moment magnets with an effective spin S=1. They display a variety of ordered magnetic structures at low temperatures, depending on the sign and relative magnitudes of the intra- and interchain exchange and any magnetic dipole–dipole interactions. We report the first preparation of the salt NH4FeBr3. Powder neutron diffraction measurements on a perdeuterated sample showed that at room temperature the unit cell is hexagonal with cell parameters a=7.398(3) Å and c=6.331(2) Å. On cooling, structural phase transitions to cells of successively lower symmetry were observed. These are probably caused by cooperative reorientations of the ND+4 tetrahedra. At 4.8(2) K and 2.8(2) K additional Bragg peaks were observed. These additional reflections were attributed to magnetic long-range order with antiferromagnetic exchange both in the basal plane and along the c axis and could be indexed on an orthorhombic unit cell of dimension 2a ×√ 3a × c. Magnetic susceptibility measurements taken with a SQUID magnetometer on a polycrystalline sample at 2–100 K with an applied magnetic field of 0.1 T showed very similar behavior to that for RbFeBr3, with a broad cusp at approximately 8 K and θ≂−43 K.

publication date

  • April 15, 1991