At high enough charge density, the homogeneous state of the D3-D7' model is
unstable to fluctuations at nonzero momentum. We investigate the end point of
this instability, finding a spatially modulated ground state, which is a charge
and spin density wave. We analyze the phase structure of the model as a
function of chemical potential and magnetic field and find the phase transition
from the homogeneous state to be first order, with a second-order critical
point at zero magnetic field.Comment: 26 pages, 16 figures; v2: refs. fixed and added; v3: refs. and
discussion added, published versio