  A quark-magnetic Ginzburg-Landau (qHGL) gradient expansion of the free energy
of two-flavor inhomogeneous quark matter in a magnetic field $H$ is derived
analytically. It can be applied away from the Lifshitz point, generalizing
standard Ginzburg-Landau techniques. The thermodynamic potential is written as
a sum of the thermal contribution, the non-thermal lowest Landau level
contribution, and the non-thermal qHGL functional, which handles any arbitrary
position-dependent periodic modulation of the chiral condensate as an input.
The qHGL approximation has two main practical features: (1) it is fast to
compute; (2) it applies to non-plane-wave modulations such as solitons even
when the amplitude of the condensate and its gradients are large (unlike
standard Ginzburg-Landau techniques). It agrees with the output of numerical
techniques based on standard regularization schemes and reduces to known
results at zero temperature ($T = 0$) in benchmark studies. It is found that
the region of the $\mu$-$T$ plane (where $\mu$ is the chemical potential)
occupied by the inhomogeneous phase expands, as $H$ increases and $T$
decreases.
