Origin of the higher order harmonics in the long-period helimagnet Cr$_{\mathrm{1/3}}$NbS$_{\mathrm{2}}$

Transition metal dichalcogenides have been shown to have a chiral, hexagonal space group. Previous SANS work by this group have found in Cr$_{\mathrm{1/3}}$NbS$_{\mathrm{2}}$ a non-centrosymmetric long-period helimagnetic structure with higher order harmonics both at zero field and in an applied field. A perfect helical state (ie sinusoidal modulation), would display no higher order peaks at zero field. Odd higher order peaks can be explained by a "squaring up" of the sin wave but not even harmonics that have been seen which implies the magnetic ground state of Cr$_{\mathrm{1/3}}$NbS$_{\mathrm{2}}$ is not completely understood.