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Up: Kenji Kojima's Ph.D. Thesis
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This chapter contains our 
SR and susceptibility measurements for the
Haldane material, Y2BaNiO5. First, in the nominally pure system, the absence of
magnetic order was confirmed with the ZF/LF-SR measurements down to
100 mK. Second, the effects of charge doping
(Y3+
Ca2+) and vacancy doping
(Ni2+Mg2+) were investigated. The charge doped system
exhibited a spin-glass like behavior in the susceptibility, while our
SR measurements revealed unconventional spin dynamics in the
milli-Kelvin regime. In the vacancy doped systems, the non-magnetic
ground state survives.
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5.1 Introduction
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5.1.1 Haldane's prediction
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5.1.2 The Valence-Bond-Solid Hamiltonian
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5.1.3 Physical Hamiltonians
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5.1.4 Experimental evidence for Haldane's conjecture
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Susceptibility
[#!RenardEPL87!#,#!RenardJAP88!#,#!GadetPRB91!#,#!AvenelPRB92!#]
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High-field magnetization [#!KatsumataPRL89!#,#!AjiroPRL89!#]
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Neutron scattering measurements
[#!RenardEPL87!#,#!RenardJAP88!#,#!MaPRB92!#,#!RegnaultPRB94!#,#!MaPRB95!#]
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Nuclear magnetic resonance (NMR)
[#!ChibaPRB91!#,#!GaveauJAP91!#,#!FujiwaraPRB92!#,#!FujiwaraPRB93!#]
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Electron spin resonance (ESR)
[#!HagiwaraPRL90!#,#!GlarumPRL91!#,#!DatePRL90!#,#!LuPRL91!#,#!BrunelPRL92!#]
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Muon spin relaxation (SR) [#!SternliebJMMM92!#,#!UemuraHI94!#]
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.
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5.2 Haldane material Y2BaNiO5
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5.3 Summary