Magnetic excitations and phonons in the spin-chain compound NaCu2O2

Abstract

We report an inelastic light scattering study of single-crystalline NaCu${}_2$O${}_2$, a spin-chain compound known to exhibit a phase with helical magnetic order at low temperatures. Phonon excitations were studied as a function of temperature and light polarization, and the phonon frequencies are compared to the results of ab-initio lattice dynamical calculations, which are also reported here. The good agreement between the observed and calculated modes allows an assignment of the phonon eigenvectors. Two distinct high-energy two-magnon features as well as a sharp low-energy one-magnon peak were also observed. These features are discussed in terms of the magnon modes expected in a helically ordered state. Their polarization dependence provides evidence of substantial exchange interactions between two closely spaced spin chains within a unit cell. At high temperatures, the spectral features attributable to magnetic excitations are replaced by a broad, quasielastic mode due to overdamped spin excitations.

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• Domain-wall excitons and optical conductivity in one-dimensional Wigner lattices
• Magnetic crossover and complex excitation spectrum of the ferromagnetic/antiferromagnetic spin-1/2 chain system alpha-TeVO4
• Raman study of spin excitations in the tunable quantum spin ladder Cu(Qnx)(Cl${}_{1-x}$Br${}_x$)${}_2$
• Bond distortion effects and electric orders in spiral multiferroic magnets