Abstract
The S=2 anisotropic triangular lattice α-NaMnO2 is studied by neutron inelastic scattering. Antiferromagnetic order occurs at T≤45 K with opening of a spin gap. The spectral weight of the magnetic dynamics above the gap (Δ≃7.5 meV) has been analyzed by the single-mode approximation. Excellent agreement with the experiment is achieved when a dominant exchange interaction (|J|/kB≃73 K), along the monoclinic b axis and a sizable easy-axis magnetic anisotropy (|D|/kB≃3 K) are considered. Despite earlier suggestions for two-dimensional spin interactions, the dynamics illustrate strongly coupled antiferromagnetic S=2 chains and cancellation of the interchain exchange due to the lattice topology. α-NaMnO2 therefore represents a model system where the geometric frustration is resolved through the lowering of the dimensionality of the spin interactions.
Original language | English |
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Article number | 077202 |
Number of pages | 4 |
Journal | Physical Review Letters |
Volume | 103 |
Issue number | 7 |
DOIs | |
Publication status | Published - 11 Aug 2009 |