Comment on ``Composite Fermion Hofstadter Problem: Partially Polarized   Density Wave States in the $\nu=2/5$ ...''
  In a recent paper [Phys.Rev.Lett. 82, 3665 (1999)], magnetic field driven spin transitions in fractional quantum Hall (FQH) states were reported, and in particular, at filling factors 2/3 and 2/5, weak features were observed at half polarization. This would imply that the ground state energy is non-monotonic at half polarization. It was proposed in   Ref.[Phys. Rev. Lett. 84, 350 (2000)] that the system is then a charge density wave (CDW) state of composite fermions with a subband gap that could explain the observed plateaus at half polarization. Similar CDW state is also expected at filling factor 2/3. Here we show that the proposed CDW state is not the half polirized ground state at these two filling factors. 
V.M. Apalkov, T. Chakraborty, P. Pietilainen, and K. Niemela