In Kittel's 8th edn. he writes, (p244) about the de Haas van Alphen effect; 'The effect can be observed in pure specimens at low temperatures in strong magnetic fields: we do not want the quantization of the electron orbits to be blurred by collisions, and we do not want the population oscillations to be averaged out by thermal populaiton of adjacent orbits' Can someone explain this? Is he saying collisions are caused by impurities or too high temperature, (or both?), or neither, and collisions are an effect of a weak magnetic field? This is what I think: the magnetic field has to be large to force Landau tubes to expand enough. The specimen must be pure and the temperature must be low for the same reason: to stop collisions, which would hinder the path of the electron, not enabling it to complete an orbit on a Landau level. Am I correct?