Magnetic Structure and Exchange Interactions in Quasi-One-Dimensional MnCl2(urea)2
Jamie L. Manson, Qingzhen Huang, Craig Brown, Jeffrey W. Lynn, Matthew B. Stone, John Singleton, Fan Xiao
MnCl2(urea)2 is a new linear chain coordination polymer that exhibits slightly counter-rotated MnCl4 rhomboids along the chain-axis. The material crystallizes in the non-centrosymmetric orthorhombic space group Iba2, with each Mn(II) ion equatorially surrounded by four Cl- that lead to bi-bridged 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 a field-induced phase transition occurring at 2.8 T. 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 reveal a Néel-type collinear ordering of Mn(II) ions with an ordered magnetic moment of 4.06(6) υB (5 υB 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 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 case of AFM-coupled FM-chains.
Mn chain compound, neutron diffraction, magnetic susceptibility, Antiferromagnetic order, high fields, inelastic magnetic scattering, exchange interactions
, Huang, Q.
, Brown, C.
, Lynn, J.
, Stone, M.
, Singleton, J.
and Xiao, F.
Magnetic Structure and Exchange Interactions in Quasi-One-Dimensional MnCl<sub>2</sub>(urea)<sub>2</sub>, Inorganic Chemistry, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=919487
(Accessed December 2, 2023)