  We study the de Gennes free energy for smectic A liquid crystals over
$\mathbb{S}^2$-valued vector fields to understand the chevron (zigzag) pattern
formed in the presence of an applied magnetic field. We identify a small
dimensionless parameter $\epsilon$, and investigate the behaviors of the
minimizers when the field strength is of order $\mathcal{O}(\epsilon^{-1})$. In
this regime, we show via $\Gamma$-convergence that a chevron structure where
the director connects two minimum states of the sphere is favored. We also
analyze the Chen-Lubensky free energy, which includes the second order gradient
of the smectic order parameter, and obtain the same general behavior as for the
de Gennes case. Numerical simulations illustrating the chevron structures for
both energies are included.
