MAGNONS AND SKYRMIONS IN FRACTIONAL HALL FERROMAGNETS

Recent experiments have established a qualitative difference between t he magnetization temperature dependences M(T) of quantum Hall ferromag nets at integer and fractional filling factors. We explain this differ ence in terms of the relative energies of collective magnon and partic le-hole excitations in the two cases. Analytic calculations for hard-c ore model systems are used to demonstrate that, in the fractional case , interactions suppress the magnetization at finite temperatures and t hat particle-hole excitations rather than long-wavelength magnons cont rol M(T) at low T. [S0163-1829(98)50940-X].