  The origin of the magnetic fields of the chemically peculiar main sequence
Ap/Bp stars is still matter of intense debate. The recent discoveries of
magnetic fields in Herbig Ae/Be stars using high resolution data obtained with
the spectropolarimeter ESPaDOnS at CFHT provide a strong argument in favour of
the fossil field hypothesis. Using a simple oblique rotator model of a centered
dipole, we fit the Stokes V LSD profiles of two of these magnetic HAeBe stars,
HD 200775 and V380 Ori, as well as their variations on timescales from days to
months. We find that in both cases the dipole hypothesis is acceptable and we
determine the rotation period, the angle between rotation and magnetic axes and
the intensity of the magnetic field at pole.
