The Heat Capacity of Cu(NO3)2·2.5H2O at Low Temperatures

Friedberg, S. A.; Raquet, C. A.

doi:10.1063/1.1656197

Cited by 47 publications

(25 citation statements)

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“…[6] There seems to be but one example available of a compound that has a specific heat which appears to follow Eq. (5.5), and that is CU(N03)' 2tH 2 0 [5]. For most compounds containing exchange-coupled dimers, 2J is so large that the overlap of the magnetic contribution with the lattice contribution is so serious as to prevent their separation and identification.…”

Section: R(j/kn2 Exp(2j/kn C=--------------~-mentioning

confidence: 98%

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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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Section: R(j/kn2 Exp(2j/kn C=--------------~-mentioning

confidence: 98%

“…Adapted from Ref. [5]. The data points should be reduced by a factor of 0.963, reducing the apparent good agreement (see Ref.…”

Section: R(j/kn2 Exp(2j/kn C=--------------~-mentioning

confidence: 99%

Introduction to Magnetic Exchange: Dimers and Clusters

Carlin

1986

Magnetochemistry

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“…The zero-field susceptibility measurement 11) had been suggesting that the system's main magnetic structure consisting of isolated dimers. Heat capacity measurements 12) and magnetization measurements 13) in the presence of a magnetic field were also carried out. However, no clear indication of a phase transition was observed.…”

Section: Early Experiments and Mean-field Theorymentioning

confidence: 99%

Critical Properties of Condensation of Field-Induced Triplet Quasiparticles

Kawashima

2005

J. Phys. Soc. Jpn.

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“…[50][51][52] These results and nuclear magnetic resonance (NMR) measurements 53 were analyzed in terms of isolated dimers with weak interdimer interactions. The first accounts of inter-dimer interactions creating a 1d system resulted from an analysis of the crystal structure, 54 and additional thermomagnetic studies.…”

Section: Copper Nitrate a Alternating Spin Chain Modelmentioning

confidence: 99%

Magnons and continua in a magnetized and dimerized spin-12chain

et al. 2014

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We examine the magnetic field dependent excitations of the dimerized spin-1/2 chain, copper nitrate, with antiferromagnetic intra-dimer exchange J1 = 0.44(1) meV and exchange alternation α = J2/J1 = 0.26(2). Magnetic excitations in three distinct regimes of magnetization are probed through inelastic neutron scattering at low temperatures. At low and high fields there are three and two long-lived magnon-like modes, respectively. The number of modes and the anti-phase relationship between the wave-vector dependent energy and intensity of magnon scattering reflect the distinct ground states: A singlet ground state at low fields µ0H < µ0Hc1 = 2.8 T and an Sz = 1/2 product state at high fields µ0H > µ0Hc2 = 4.2 T. In the intermediate field regime, a continuum of scattering forhω ≈ J1 is indicative of a strongly correlated gapless quantum state without coherent magnons.

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The Heat Capacity of Cu(NO3)2·2.5H2O at Low Temperatures

Cited by 47 publications

References 5 publications

Introduction to Magnetic Exchange: Dimers and Clusters

Introduction to Magnetic Exchange: Dimers and Clusters

Critical Properties of Condensation of Field-Induced Triplet Quasiparticles

Magnons and continua in a magnetized and dimerized spin-12chain

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