  We have studied the effect of structural disorder on the de Haas van Alphen
(dHvA) and Shubnikov de Haas (SdH) quantum oscillations measured in
single-crystal and highly oriented pyrolytic graphite samples at temperatures
down to 30 mK and at magnetic fields up to 14 T. The measurements were
performed on different samples characterized by means of x-ray diffraction,
transmission electron microscopy and atomic-force microscopy techniques. Our
results reveal a correlation between the amplitude of quantum oscillations and
the surface roughness.
