  We examine the influence of bidirectional anchoring on the unwinding of a
planar cholesteric liquid crystal induced by the application of a magnetic
field. We consider a liquid crystal layer confined between two plates with the
helical axis perpendicular to the substrates. We fixed the director twist on
one boundary and allow for bidirectional anchoring on the other by introducing
a high-order surface potential. By minimizing the total free energy for the
system, we investigate the untwisting of the cholesteric helix as the liquid
crystal attempts to align with the magnetic field. The transitions between
metastable states occur as a series of pitchjumps as the helix expels quarter
or half-turn twists, depending on the relative sizes of the strength of the
surface potential and the bidirectional anchoring. We show that secondary easy
axis directions can play a significant role in the unwinding of the cholesteric
in its transition towards a nematic, especially when the surface anchoring
strength is large.
