Search results for "Antiferromagnet"
showing 10 items of 506 documents
One-dimensional iron(III) and two-dimensional iron(III)nickel(II) cyanide-bridged ferromagnetic arrays from hexacyanoferrate(III) and [Ni(cyclam)]2+ …
1999
Abstract The X-ray structures and magnetic properties of a iron(III) linear chain and a honeycomb-like layered iron(III)-nickel(II) cyanide-bridged compound are reported. The former contains alternating iron sites and unexpected ferromagnetic behaviour, justified on the basis of the axial distortion from regular octahedral geometry of one of the iron ions. The latter is metamagnetic with ferromagnetic intralayers and antiferromagnetic interlayers interactions with a Neel temperature, TN= 7.7 K. The field-induced transition from an antiferro- to a ferromagnetic state takes place at Hc= 5000 G. The antiferromagnetic ordered phase exhibits spin-canting and long range ferromagnetic ordering at …
A stable oxoverdazyl free radical: Structural and magnetic characterization
2006
Abstract The structure and magnetic properties (susceptibility and ESR) of the stable oxoverdazyl free radical 6-(4-acetamidophenyl)-1,4,5,6-tetrahydro-2,4-dimethyl-1,2,4,5-tetrazin-3(2H)-one are presented. The crystal structure consists of chains of parallel planar molecules running along the b-axis. These chains are formed by dimers with a ring-over-bond overlap and a significant offset between dimers, although with similar inter- and intradimer distances. The susceptibility measurements show that this compound is an S = 1/2 paramagnet with weak antiferromagnetic interactions. The magnetic susceptibility can be very well reproduced with an antiferromagnetic regular chain model with g = 2.…
Polyoxometalates: From Magnetic Models to Multifunctional Materials
2002
In this article we have presented some recent achievements of the polyoxometalates in the fields of molecular magnetism and functional molecular materials. In the context of the molecular magnetism we have shown that POMs provide ideal examples of magnetic clusters with coexisting ferro and antiferromagnetic exchange interactions which can be investigated using a variety of magnetic techniques, including the Inelastic Neutron Scattering spectroscopy, to get a thorough characterization of the magnetic levels in these large clusters, and to test the validity of the spin hamiltonians commonly used in magnetism.
Ab initio Hartree-Fock calculations of LaMnO3 (110) surfaces
2003
We present the results of ab initio Hartree-Fock calculations of the LaMnO3 (110) surface. Using seven-plane slabs, periodic in 2D and containing three formula units, we compare the properties of a stoichiometric surface with oxygen vacancies, and non-stoichiometric, defect-free surfaces, analyze the dispersion of the effective charges near the surface, and calculate the surface energy before and after relaxation, for both ferromagnetric and antiferromagnetic spin orderings in a slab. q 2003 Elsevier Ltd. All rights reserved.
Neutron diffraction studies of the molecular compound [Co 2(bta)]n (H4bta =1,2,4,5-benzenetetracarboxylic acid): In the quest of canted ferromagnetism
2013
The exchange mechanism and magnetic structure of the organic-inorganic layered molecule-based magnet [Co2(bta)]n (1) (H 4bta =1,2,4,5-benzenetetracarboxylic acid) have been investigated through variable-temperature magnetic susceptibility measurements and supported with a series of neutron diffraction experiments. Cryomagnetic studies have shown an antiferromagnetic ordering at a transition temperature of 16 K that is followed by the appearance of a weak ferromagnetism below 11 K. The weak antiferromagnetic interlayer interaction plays an important role in this system in spite of the long interlayer separation. A ferromagnetic ordering is induced by applied magnetic fields greater than 1800…
Structure and Properties of GdAuSn and the GdAuSn/MnAuSn System
2006
The crystal structure of GdAuSn was refined by means of single crystal X-ray diffraction. Band structure calculations based on the structural data confirmed the antiferromagnetic ground state and the metallic behaviour of GdAuSn. 119mSn, 155Gd and 197Au Mossbauer spectroscopic studies were used to verify the values of the hyperfine parameters that were given by the band structure calculations. Band structure calculations of MnAuSn confirmed that this half-Heusler compound belongs to the family of half-metallic ferromagnets. Magnetic susceptibility, conductivity and Mossbauer studies were used to characterize granular material based on the half-Heusler ferromagnet MnAuSn in the antiferromagn…
Syntheses, Structures, Magnetic Properties, and Density Functional Theory Magneto-Structural Correlations of Bis(μ-phenoxo) and Bis(μ-phenoxo)-μ-acet…
2013
The bis(mu-phenoxo) (FeNiIII)-Ni-II compound [Fe-III(N-3)(2)LNiII(H2O)(CH3CN)](ClO4) (1) and the bis(mu-phenoxo)-mu-acetate/bis(mu-phenoxo)-bis(mu-acetate) (FeNiII)-Ni-III compound {[Fe-III(OAc)LNiII(H2O)(mu-OAc)](0.6)center dot[(FeLNiII)-L-III(mu-OAc)(2)](0.4)}(ClO4)center dot 1.1H(2)O (2) have been synthesized from the Robson type tetraiminodiphenol macrocyclic ligand H2L, which is the [2 + 2] condensation product of 4-methyl-2,6-diformylphenol and 2,2'-dimethy1-1,3-diaminopropane. Single-crystal X-ray structures of both compounds have been determined. The cationic part of the dinuclear compound 2 is a cocrystal of the two species [Fe-III(OAc)LNiII(H2O)(mu-OAc)](+) (2A) and [(FeLNiII)-L-I…
Coordination polymers based on bridging cyanocarbanions and bis-tridentate p-phenylenediamine ligands
2017
Two new Cu(II) coordination polymeric neutral chains of formula [Cu 2 (1,4-tpbd)(μ-A) 2 (H 2 O) 2 ](A) 2 with A = tcnoet − ( 1 ) and tcnopr − ( 2 ) (1,4-tpbd = N,N,N′N′ -tetrakis(2-pyridylmethyl)benzene-1,4-diamine, tcnoet − = 1,1,3,3-tetracyano-2-ethoxypropenide and tcnopr − = 1,1,3,3-tetracyano-2-propoxypropenide) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction and magnetic measurements. 1 and 2 show alternating chains where the 1,4-tpbd and the cyanocarbanion units (tcnoet − for 1 and tcnopr − for 2 ) alternate as bridging ligands. The molecular structure can be viewed as [Cu 2 (μ-tpbd)] 4+ dinuclear units (with Cu⋯Cu distances of 8.2233(3) for 1 …
A Copper(II)-Cytidine Complex as a Building Unit for the Construction of an Unusual Three-Dimensional Coordination Polymer
2010
The chiral [Cu(cyd) 4 ] 6- anion acts as a multiarmed complex-ligand toward auxiliary copper(II) centers leading to the first example of cytidinate-bridged three-dimensional (3D) coordination polymer of formula [Cu 6 (H 2 O) 7 (ClO 4 ) 3 Cu(cyd) 4 ]-(ClO 4 ) 3 (1). Single crystal X-ray analysis of 1 shows a unique 3D covalent network supported by the exclusive hypercoordination of the cytidinate ligand that bridges four crystallographically independent copper(II) ions via the N3, O2, O2', O3', and O5' set of atoms. Magnetic susceptibility measurements in the temperature range 1.9-295 K reveal the coexistence of ferro- and antiferromagnetic interactions within the hexacopper(II) core of 1, t…
One-dimensional oxalato-bridged copper(II) complex possessing two structurally different metallic centres
2001
Abstract The crystal structure of the oxalato-bridged copper(II) compound [Cu2(μ-ox)2(ampy)3]n 1 (ox=oxalate dianion, ampy=2-amino-3-methylpyridine) consists of infinite corrugated one-dimensional chains in which two types of copper(II) centres, five- and six-coordinated, are bridged sequentially by asymmetric bis-bidentate oxalato ligands. Magnetic susceptibility measurements show the occurrence of a significant intrachain antiferromagnetic coupling (J=−22.9 cm −1 ) .