Anomalous frequency and intensity scaling of collective and local modes in a coupled spin tetrahedron system

Abstract

We report on the magnetic excitation spectrum of the coupled spin tetrahedral system Cu${}_2$Te${}_2$O${}_5$Cl${}_2$ using Raman scattering on single crystals. The transition to an ordered state at T${}_N^{Cl}$=18.2 K evidenced from thermodynamic data leads to the evolution of distinct low-energy magnetic excitations superimposed by a broad maximum. These modes are ascribed to magnons with different degree of localization and a two-magnon continuum. Two of the modes develop a substantial energy shift with decreasing temperature similar to the order parameter of other Neel ordered systems. The other two modes show only a negligible temperature dependence and dissolve above the ordering temperature in a continuum of excitations at finite energies. These observations point to a delicate interplay of magnetic inter- and intra-tetrahedra degrees of freedom and an importance of singlet fluctuations in describing a spin dynamics.

arXiv comment7pages, 6figures, 1table

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Cited by in corpus (3)

• Raman scattering in a Heisenberg S=1/2 antiferromagnet on the anisotropic triangular lattice
• Persistence of singlet fluctuations in the coupled spin tetrahedra system Cu2Te2O5Br2 revealed by high-field magnetization and 79Br NQR - 125Te NMR
• Parity-dependent phase diagrams in spin-cluster two-leg ladders