Azurite (Cu3(CO3)2(OH)2) is a model substance of a diamond spin chain, one of frustrated antiferromagnetic quantum spin chains. The high field magnetization up to 60 T, magnetic susceptibility, ...magnetic entropy, muon spin relaxation and 1H-NMR of azurite have been measured using single crystals. A distinct 1/3 magnetization plateau is confirmed to be present in the magnetization curve. Two resonance peaks of 1H-NMR were observed. By analyzing temperature dependencies of their hyperfine shift, we found two different local susceptibilities which correspond to susceptibility of dimer and monomer spins, respectively. New field induced phase transition was found to occur at a critical field where the magnetic plateau onsets. A short range magnetic ordering developed in a peculiar two-stage process, which was revealed by temperature dependence of the magnetic specific heat and susceptibility.
Cu
3(CO
3)
2(OH)
2 (azurite), in which
Cu
2+
(S=
1
2
)
monomers and dimers are arranged alternately along the
b-axis to make an infinite chain, is regarded as an actual material for the frustrated ...diamond chain model. we have measured magnetic susceptibility, high field magnetization and
1
H
NMR of a natural mineral single crystal of azurite to investigate the magnetic properties. The experimental results were compared with the theoretical expectation to suggest the ground state of Cu
3(CO
3)
2(OH)
2 is in a gapless phase.
We have performed magnetic susceptibility and 51V NMR experiments with CaV2O4, a model substance for a frustrated S=1 spin chain with competing nearest neighbor (NN) and next-nearest neighbor (NNN) ...antiferromagnetic interactions. We report on the analysis of the magnetic susceptibility and the 51V NMR experiments suggesting a gapless nature of CaV2O4. The absence of a spin gap is in clear contrast to the case of a non-frustrated spin chains which usually have a Haldane gap.
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