  The magnetic phase diagrams of RMnO3 (R = Er, Yb, Tm, Ho) are investigated up
to 14 Tesla via magnetic and dielectric measurements. The stability range of
the AFM order below the Neel temperature of the studied RMnO3 extends to far
higher magnetic fields than previously assumed. Magnetic irreversibility
indicating the presence of a spontaneous magnetic moment is found near 50 K for
R=Er, Yb, and Tm. At very low temperatures and low magnetic fields the phase
boundary defined by the ordering of the rare earth moments is resolved. The
sizable dielectric anomalies observed along all phase boundaries are evidence
for strong spin-lattice coupling in the hexagonal RMnO3. In HoMnO3 the strong
magnetoelastic distortions are investigated in more detail via magnetostriction
experiments up to 14 Tesla. The results are discussed based on existing data on
magnetic symmetries and the interactions between the Mn-spins, the rare earth
moments, and the lattice.
