Spin excitations from a partially populated composite fermion level are
studied above and below ν=1/3. In the range 2/7<ν<2/5 the experiments
uncover significant departures from the non-interacting composite fermion
picture that demonstrate the increasing impact of interactions as quasiparticle
Landau levels are filled. The observed onset of a transition from free to
interacting composite fermions could be linked to condensation into the higher
order states suggested by transport experiments and numerical evaluations
performed in the same filling factor range.Comment: 4 pages, 5 figures, to appear in PR