title: Magnetic Structure and Exchange Interactions in Quasi-One-Dimensional MnCl2(urea)2.
abstract: MnCl2(urea)2 is a new linear chain coordination polymer that exhibits slightly counter-rotated Mn2Cl2 rhomboids along the chain-axis. The material crystallizes in the noncentrosymmetric orthorhombic space group Iba2, with each Mn(II) ion equatorially surrounded by four Cl(-) that lead to bibridged ribbons. Urea ligands coordinate via O atoms in the axial positions. Hydrogen bonds of the Cl···H-N and O···H-N type link the chains into a quasi-3D network. Magnetic susceptibility data reveal a broad maximum at 9 K that is consistent with short-range magnetic order. Pulsed-field magnetization measurements conducted at 0.6 K show that a fully polarized magnetic state is achieved at Bsat = 19.6 T with another field-induced phase transition occurring at 2.8 T. Zero-field neutron diffraction studies made on a powdered sample of MnCl2(urea)2 reveal that long-range magnetic order occurs below TN = 3.2(1) K. Additional Bragg peaks due to antiferromagnetic (AFM) ordering can be indexed according to the Ib'a2' magnetic space group and propagation vector τ = [0, 0, 0]. Rietveld profile analysis of these data revealed a Néel-type collinear ordering of Mn(II) ions with an ordered magnetic moment of 4.06(6) μB (5 μB is expected for isotropic S = (5)/2) oriented along the b-axis, i.e., perpendicular to the chain-axis that runs along the c-direction. Owing to the potential for spatial exchange anisotropy and the pitfalls in modeling bulk magnetic data, we analyzed inelastic neutron scattering data to retrieve the exchange constants: Jc = 2.22 K (intrachain), Ja = -0.10 K (interchain), and D = -0.14 K with J > 0 assigned to AFM coupling. This J configuration is most unusual and contrasts the more commonly observed AFM interchain coupling of 1D chains.
authors.affiliation: Department of Chemistry and Biochemistry, Eastern Washington University , Cheney, Washington 99004, United States.
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Manson
authors.affiliation: NISTCenter for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Qing-Zhen
authors.initials: QZ
authors.lastname: Huang
authors.affiliation: NISTCenter for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.|Department of Chemical and Biochemical Engineering, University of Delaware , Newark, Delaware 19716, United States.
authors.forename: Craig M
authors.initials: CM
authors.lastname: Brown
authors.affiliation: NISTCenter for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Lynn
authors.affiliation: Quantum Condensed Matter Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37830, United States.
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Stone
authors.affiliation: National High Magnetic Field Laboratory, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: John
authors.initials: J
authors.lastname: Singleton
authors.affiliation: Center for Materials Physics, Durham University , Durham DH1 3LE, United Kingdom.
authors.forename: Fan
authors.initials: F
authors.lastname: Xiao