Published online by Cambridge University Press: 12 April 2016
We report first results of our systematic investigation of the magnetic field structure of rotating single magnetic white dwarfs and of white dwarfs in magnetic cataclysmic variables. The global magnetic field distributions on the isolated white dwarf HE 1045-0908 and the accreting white dwarfs in EF Eri and CP Tuc have been derived from phase-resolved flux and polarization spectra obtained with FORS1 at the ESO VLT using the systematic method of Zeeman tomography.