  Today, one of the greatest challenges concerning the Ap/Bp stars is to
understand the origin of their slow rotation and their magnetic fields. The
favoured hypothesis for the latter is the fossil field, which implies that the
magnetic fields subsist throughout the different evolutionary phases, and in
particular during the pre-main sequence phase. The existence of magnetic fields
at the pre-main sequence phase is also required to explain the slow rotation of
Ap/Bp stars. However, until recently, essentially no information was available
about the magnetic properties of intermediate-mass pre-main sequence stars, the
so-called Herbig Ae/Be stars. The new high-resolution spectropolarimeter
ESPaDOnS, installed in 2005 at the Canada-France-Hawaii telescope, provided the
capability necessary to perform surveys of the Herbig Ae/Be stars in order to
investigate their magnetism and rotation. These investigations have resulted in
the detection and/or confirmation of magnetic fields in 8 Herbig Ae/Be stars,
ranging in mass from 2 to nearly 15 solar masses. In this contribution I will
present the results of our survey, as well as their implications for the origin
and evolution of the magnetic fields and rotation.

Astrophysics