title: Antiferromagnetism in a Family of S = 1 Square Lattice Coordination Polymers NiX2(pyz)2 (X = Cl, Br, I, NCS; pyz = Pyrazine).
abstract: The crystal structures of NiX2(pyz)2 (X = Cl (1), Br (2), I (3), and NCS (4)) were determined by synchrotron X-ray powder diffraction. All four compounds consist of two-dimensional (2D) square arrays self-assembled from octahedral NiN4X2 units that are bridged by pyz ligands. The 2D layered motifs displayed by 1-4 are relevant to bifluoride-bridged [Ni(HF2)(pyz)2]EF6 (E = P, Sb), which also possess the same 2D layers. In contrast, terminal X ligands occupy axial positions in 1-4 and cause a staggered packing of adjacent layers. Long-range antiferromagnetic (AFM) order occurs below 1.5 (Cl), 1.9 (Br and NCS), and 2.5 K (I) as determined by heat capacity and muon-spin relaxation. The single-ion anisotropy and g factor of 2, 3, and 4 were measured by electron-spin resonance with no evidence for zero-field splitting (ZFS) being observed. The magnetism of 1-4 spans the spectrum from quasi-two-dimensional (2D) to three-dimensional (3D) antiferromagnetism. Nearly identical results and thermodynamic features were obtained for 2 and 4 as shown by pulsed-field magnetization, magnetic susceptibility, as well as their Néel temperatures. Magnetization curves for 2 and 4 calculated by quantum Monte Carlo simulation also show excellent agreement with the pulsed-field data. Compound 3 is characterized as a 3D AFM with the interlayer interaction (J⊥) being slightly stronger than the intralayer interaction along Ni-pyz-Ni segments (J(pyz)) within the two-dimensional [Ni(pyz)2](2+) square planes. Regardless of X, J(pyz) is similar for the four compounds and is roughly 1 K.
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Junjie
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Physics, University of Warwick , Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Goddard
authors.affiliation: National High Magnetic Field Laboratory, Los Alamos National Laboratory , MS-E536, Los Alamos, New Mexico 87545, United States.
authors.forename: John
authors.initials: J
authors.lastname: Singleton
authors.affiliation: Department of Physics, University of Warwick , Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom.
authors.forename: Jamie
authors.initials: J
authors.lastname: Brambleby
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Francesca
authors.initials: F
authors.lastname: Foronda
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Johannes S
authors.initials: JS
authors.lastname: Möller
authors.affiliation: National High Magnetic Field Laboratory, Los Alamos National Laboratory , MS-E536, Los Alamos, New Mexico 87545, United States.
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Kohama
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Saman
authors.initials: S
authors.lastname: Ghannadzadeh
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Arzhang
authors.initials: A
authors.lastname: Ardavan
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Blundell
authors.affiliation: Centre for Materials Physics, Durham University , South Road, Durham DH1 3LE, United Kingdom.
authors.forename: Tom
authors.initials: T
authors.lastname: Lancaster
authors.affiliation: Centre for Materials Physics, Durham University , South Road, Durham DH1 3LE, United Kingdom.
authors.forename: Fan
authors.initials: F
authors.lastname: Xiao
authors.affiliation: Centre for Materials Physics, Durham University , South Road, Durham DH1 3LE, United Kingdom.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Williams
authors.affiliation: ISIS Pulsed Muon Facility, STFC Rutherford Appleton Laboratory , Chilton, Didcot, OX11 0QX, United Kingdom.
authors.forename: Francis L
authors.initials: FL
authors.lastname: Pratt
authors.affiliation: ISIS Pulsed Muon Facility, STFC Rutherford Appleton Laboratory , Chilton, Didcot, OX11 0QX, United Kingdom.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Baker
authors.affiliation: School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371, Singapore.
authors.forename: Keola
authors.initials: K
authors.lastname: Wierschem
authors.affiliation: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory , Lemont, Illinois 60439, United States.
authors.forename: Saul H
authors.initials: SH
authors.lastname: Lapidus
authors.affiliation: Department of Physics and Astronomy, State University of New York , Stony Brook, New York 11794, United States.
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Stone
authors.affiliation: Department of Physics and Astronomy, State University of New York , Stony Brook, New York 11794, United States.
authors.forename: Peter W
authors.initials: PW
authors.lastname: Stephens
authors.affiliation: Department of Chemistry, University of Copenhagen , Copenhagen DK-2100, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Bendix
authors.affiliation: Department of Chemistry and Biochemistry, Eastern Washington University , Cheney, Washington 99004, United States.
authors.forename: Toby J
authors.initials: TJ
authors.lastname: Woods
authors.affiliation: Department of Chemistry and Biochemistry, Eastern Washington University , Cheney, Washington 99004, United States.
authors.forename: Kimberly E
authors.initials: KE
authors.lastname: Carreiro
authors.affiliation: Department of Chemistry and Biochemistry, Eastern Washington University , Cheney, Washington 99004, United States.
authors.forename: Hope E
authors.initials: HE
authors.lastname: Tran
authors.affiliation: Department of Chemistry and Biochemistry, Eastern Washington University , Cheney, Washington 99004, United States.
authors.forename: Cecelia J
authors.initials: CJ
authors.lastname: Villa
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