Magnetic behavior of copper diethyldithiocarbamate at low temperatures: A reinvestigation

Duyneveld́t, A.J. van; Santen, J.A. van; Carlin, Richard L.

doi:10.1016/0009-2614(76)80046-2

Cited by 9 publications

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“…If 2J were positive, the If such large ferromagnetic interactions were important in Cu(dtch, the result should be apparent in susceptibility data taken to low temperatures [53].…”

Section: Some Other Dimersmentioning

confidence: 95%

Introduction to Magnetic Exchange: Dimers and Clusters

Carlin

1986

Magnetochemistry

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Energy Levels and Specific Heats 71configurational mixing of states such as M+ F M2+. The electron on Fin (c) and (d) can now couple with the lone electron in a d z 2 orbital on an adjoining Ni2+ . The preferred coupling is to give a singlet state [(c), called antiferromagnetic] rather than a triplet, (d). This in turn stabilizes the singlet state (a) with respect to the triplet (b). The strength of the interaction will depend on the amount of overlap, and we present here only a model of 180° superexchange. Metal ion orbitals can also overlap with p" ligand orbitals at a 90° angle, and much recent research effort has gone into finding the factors which influence this superexchange interaction.This model, which has been applied to a variety of systems [1,2] is somewhat similar to that which is used for explaining spin-spin coupling in NMR spectroscopy [3]. The Hamiltonian in use for metal-metal exchange interaction in magnetic insulators is of the form (5.2) where the sum is taken over all pair-wise interactions of spins i and j in a lattice. For the moment, we shall restrict our attention to dimers, and thereby limit the summation to the two atoms 1 and 2 in the dimeric molecule, so thatThis is called an isotropic (note the dot product between the two spins, S) or Heisenberg Hamiltonian, and we adopt the convention that negative J refers to antiferromagnetic (spin-paired or singlet ground state in a dimer) interactions, and positive J refers to ferromagnetic (spin-triplet ground state) interactions. The exchange constant J is given in energy units (Kelvins) and measures the strength ofthe interaction. The reader must be careful in comparing different authors, for a variety of conventions (involving the negative sign and even the factor of 2) are in use. (The symbol J now takes a different meaning from its earlier use as the quantum operator for total angular momentum.) Energy Levels and Specific HeatsAn antiferromagnetic interaction ofthe type given in Eq. (5.3), when applied to two ions each of!/ = t gives a spin-singlet ground state and a spin-triplet 2J in energy above the singlet ( Fig. 5.2). Naturally, ifthe interaction were ferromagnetic, the diagram is simply inverted. For an external field applied along the z-axis of the pair, the complete Hamiltonian will be taken as

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“…If 2J were positive, the If such large ferromagnetic interactions were important in Cu(dtch, the result should be apparent in susceptibility data taken to low temperatures [53].…”

Section: Some Other Dimersmentioning

confidence: 95%