The phonon excitations of fractional quantum Hall (FQH) states at filling factors ν =1÷3,2÷5, 4÷7, 3÷5, 4÷3, and 5÷3 were investigated. The excitations were found to be based on Landau-level transitions of composite fermions (CF). It was observed that at filling factor ν = 2÷3, a linear field dependence of the excitation energy in the high field regime showed a spin transition, which was excited by the phonons. All the transport gaps, except the one measured at ν = 2÷3, were found to be lower than the phonon excitation gaps due to disorder effects and because temperature was also coupled to spin flip excitations.
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