  de Haas-van Alphen oscillation spectrum of two-dimensional systems is studied
for general power law energy dispersion, yielding a Fermi surface area of the
form $S(E)\propto E^\alpha$ for a given energy $E$. The case $\alpha=1$ stands
for the parabolic energy dispersion. It is demonstrated that the periodicity of
the magnetic oscillations in inverse field can depend notably on the
temperature. We evaluated analytically the Fourier spectrum of these
oscillations to evidence the frequency shift and smearing of the main peak
structure as the temperature increases.
