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Register a new userObservation of three-magnon light scattering in CuGeO_3
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Added by
Paul van Loosdrecht
Publication date
1997
fields
Physics
and research's language is
English
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Temperature and magnetic field dependent polarized Brillouin spectra of CuGeO_3 are reported. In addition to a bound singlet state at 30 cm^{-1}, a new feature has been observed at 18 cm^{-1}. This feature is interpreted in terms of a novel three-magnon light scattering process between excited triplet states.
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The effects of interchain coupling on solitons and soliton lattice structures in CuGeO3 are explored. It is shown that interchain coupling substantially increases the soliton width and changes the soliton lattice structures in the incommensurate phase. It is proposed that the experimentally observed large soliton width in CuGeO3 is mainly due to interchain coupling effects.
We measure by inelastic neutron scattering the spin excitation spectra as a function of applied magnetic field in the quantum spin-ladder material (C5H12N)2CuBr4. Discrete magnon modes at low fields in the quantum disordered phase and at high fields in the saturated phase contrast sharply with a spinon continuum at intermediate fields characteristic of the Luttinger-liquid phase. By tuning the magnetic field, we drive the fractionalization of magnons into spinons and, in this deconfined regime, observe both commensurate and incommensurate continua.
Although the parent iron-based pnictides and chalcogenides are itinerant antiferromagnets, the use of local moment picture to understand their magnetic properties is still widespread. We study magnetic Raman scattering from a local moment perspective for various quantum spin models proposed for this new class of superconductors. These models vary greatly in the level of magnetic frustration and show a vastly different two-magnon Raman response. Light scattering by two-magnon excitations thus provides a robust and independent measure of the underlying spin interactions. In accord with other recent experiments, our results indicate that the amount of magnetic frustration in these systems may be small.
The ferrimagnetic spinels MnB2O4 (B = Mn,V) exhibit a similar series of closely spaced magnetic and structural phase transitions at low temperatures, reflecting both magnetic frustration and a strong coupling between the spin and lattice degrees of freedom. Careful studies of excitations in MnB2O4 (B = Mn,V), and the evolution of these excitations with temperature, are important for obtaining a microscopic description of the role that magnetic excitations and spin-lattice coupling play in the low temperature phase transitions of these materials. We report an inelastic light (Raman) scattering study of the temperature and magnetic field dependences of one- and two-magnon excitations in MnV2O4 and Mn3O4. We observe a pair of q=0 one-magnon modes at 74 cm^{-1} and 81 cm^{-1} in MnV2O4, which is in contrast with the single 80 cm^{-1} q=0 magnon that has been reported for MnV2O4 based on previous neutron scattering measurements and spin wave calculations. Additionally, we find that the two-magnon energy of MnV2O4 decreases (softens) with decreasing temperature below T_{N}, which we attribute to strong coupling between magnetic and vibrational excitations near the zone boundary.
Some of the properties of the low-dimensional electronically correlated materials cgo and vo are discussed. The emphasis lies on recent results obtained using Raman scattering and optical absorption spectroscopy as a function of temperature, magnetic field and hydrostatic pressure.
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