Search results for "exchange interaction"

A black-box approach to the construction of metal-radical multispin systems and analysis of their magnetic properties

2020

An interaction of M(hfac)2 (M = Mn or Ni) with N-(bis(4,4,5,5-tetramethyl-3-oxido-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)methylene)-2-methyl-propan-2-amine oxide (a nitronyl nitroxide diradical with theC[double bond, length as m-dash]N(O)-tert-Bu coupler) was investigated under various conditions. It was found that prolongation of reaction time caused transformation of the initial diradical into new diradicals with the uniqueC[double bond, length as m-dash]N-OH coupling unit and formation of binuclear Mn(ii) and Ni(ii) complexes, which were characterized by X-ray diffraction analysis. The resulting binuclear heterospin complexes have a complicated magnetic structure with six paramagnetic cente…

Magnetic field-controlled 0−π transitions and their experimental signatures in superconductor-ferromagnet-superconductor junctions

2019

Superconductor-ferromagnet-superconductor Josephson junctions are known to exist in the $0$ and $\pi$ states with the transitions between them controlled by the temperature and ferromagnetic interlayer thickness. We demonstrate that these transitions can be controlled also by the external magnetic field directed perpendicular to the layers. By varying the ratio of diffusion coefficients in superconducting and ferromagnetic layers, these field-controlled transitions can be made detectable for arbitrary large value of the exchange energy in the ferromagnet. We also show that the $0$-$\pi$ transitions in the perpendicular field can be observed as the specific features of the flux-flow conducti…

1D antiferromagnetism in spin‐alternating bimetallic chains

1990

The magnetic and thermal properties of the ordered bimetallic chain CoNi(EDTA)⋅6H2O in the very low‐temperature range are reported. The magnetic behavior does not exhibit the characteristic features of 1D ferrimagnets, but a continuous decrease of χmT towards zero at absolute zero. This 1D antiferromagnetic behavior results from an accidental compensation between the moments located at the two sublattices. This behavior, as well as the specific‐heat results, are modeled on the basis of an Ising‐exchange model that considers both alternating spins and Landé factors, and a zero‐field splitting on the Ni site. Eugenio.Coronado@uv.es ; Fernando.Sapina@uv.es

The ferrimagnetic compounds CoM[M’(EDTA)]2⋅4H2O(M,M’=Co,Ni): Magnetic characterization of CoCo[Ni(EDTA)2]⋅4H2O

1990

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Magnetic exchange interactions in the heteropoly complexes [M4(H2O)2(PW9O34)2]10− [M=Co(II) and Cu(II)]

1990

The magnetic properties of the heteropolyanions [M4(H2O)2(PW9O34)2]10− [M=Co(II) and Cu(II)] down to 4 K are reported. Their individual heteropoly molecules contain a rhomblike arrangement formed by four coplanar MO6 octahedra sharing edges. The magnetic properties support an intramolecular ferromagnetic exchange in the Co(II) tetramer, and antiferromagnetic exchange in the Cu(II) tetramer. These behaviors are discussed assuming anisotropic exchange in the Co(II) compound, and Heisenberg exchange in the Cu(II) compound. Carlos.Gomez@uv.es

Uncompensated magnetization in the layered molecular antiferromagnet {N(n-C5H11)4[MnIIFeIII(ox)3]}∞

2009

Abstract Studies on the magnetic properties of the molecular antiferromagnetic material {N( n -C 5 H 11 ) 4 [Mn II Fe III (ox) 3 ]} ∞ , carried out by various physical techniques (AC/DC magnetic susceptibility, magnetization, heat capacity measurements and Mossbauer spectroscopy) at low temperatures, have been presented. Different experimental observations complement each other and provide a clue for the observation of an uncompensated magnetization below the Neel temperature and short-range correlations persisting high above T N . It is understood that the honeycomb layered structure of the compound contains non-equivalent magnetic sub-lattices, (Mn II –ox–Fe III A –...) and (Mn II –ox–Fe …

Coordination Complexes of a Neutral 1,2,4-Benzotriazinyl Radical Ligand: Synthesis, Molecular and Electronic Structures, andMagnetic Properties

2015

A series of d-block metal complexes of the recently reported coordinating neutral radical ligand 1-phenyl-3-(pyrid-2-yl)-1,4-dihydro-1,2,4-benzotriazin-4-yl (1) was synthesized. The investigated systems contain the benzotriazinyl radical 1 coordinated to a divalent metal cation, MnII, FeII, CoII, or NiII, with 1,1,1,5,5,5-hexafluoroacetylacetonato (hfac) as the auxiliary ligand of choice. The synthesized complexes were fully characterized by single-crystal X-ray diffraction, magnetic susceptibility measurements, and electronic structure calculations. The complexes [Mn(1)(hfac)2] and [Fe(1)(hfac)2] displayed antiferromagnetic coupling between the unpaired electrons of the ligand and the meta…

Magnetism and EPR spectra of the two‐sublattice manganese chain Mn2(EDTA)⋅9H2O

1990

We report on the magnetic behavior and single‐crystal EPR spectra of the chain complex Mn2(EDTA)⋅9H2O characterized by two different alternating sites for the manganese ions. Magnetic susceptibility data are indicative of weak antiferromagnetic exchange interactions between the manganese ions, showing a maximum of about 3 K. This behavior can be accurately described on the basis of a Heisenberg chain model that assumes classical spins, giving J/k=−0.72 K and g=2.0. The EPR spectra are typically low dimensional, with an angular dependence of the linewidth of the type (3 cos2 θ−1)n (n=4/3 or 2). Nevertheless, such a behavior cannot be reproduced from a one‐dimensional model with dipolar broad…

Ein neuartiges Polyoxowolframat mit einemtriangulo-NiII3-Cluster mit ferromagnetischen Austauschwechselwirkungen und einemS = 3-Grundzustand

1992

Small clusters with Heisenberg antiferromagnetic exchange

2000

We study small symmetrical clusters of magnetic ions with Heisenberg antiferromagnetic exchange interaction. We calculate the magnetization and the specific heat as functions of applied magnetic field at zero and non-zero temperature. Results are given for both classical and quantum systems. At zero temperature the classical systems undergo a series of transitions where the symmetry changes as a function of applied field. The quantum systems show similar features to Ising systems previously studied.