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キーワード:
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要旨:
The magnetic response of antiferromagnetic CsO2, coming from the
p-orbital S = 1/2 spins of anionic O-2(-) molecules, is followed by
Cs-133 nuclear magnetic resonance across the structural phase transition
occurring at T-s1 = 61 K on cooling. Above T-s1, where spins form a
square magnetic lattice, we observe a huge, nonmonotonic temperature
dependence of the exchange coupling originating from thermal librations
of O-2(-) molecules. Below T-s1, where antiferromagnetic spin chains are
formed as a result of p-orbital ordering, we observe a spin
Tomonaga-Luttinger-liquid behavior of spin dynamics. These two
interesting phenomena, which provide rare simple manifestations of the
coupling between spin, lattice, and orbital degrees of freedom,
establish CsO2 as a model system for molecular solids.
