Spin excitations in the Fractional Quantum Hall regime at $\nu \lesssim 1\mathrm{/}3$

We report inelastic light scattering experiments in the fractional quantum Hall regime at filling factors $\nu \lesssim 1\mathrm{/}3$. A spin mode is observed below the Zeeman energy. The filling factor dependence of the mode energy is consistent with its assignment to spin flip excitations of composite fermions with four attached flux quanta ($\varphi$=4). Our findings reveal a composite fermion Landau level structure in the $\varphi$=4 sequence.