Untwisting of a soft ferrocholesteric liquid crystal by shear flow and magnetic field

We theoretically study the effect of a shear flow and a uniform magnetic field on the helical structure of a ferrocholesteric liquid crystal with the finite anchoring between the liquid-crystalline matrix and magnetic particles (soft ferrocholesteric). The axis of the ferrocholesteric helix is orthogonal to the plane of the shear flow and the magnetic field. We derive the integral expressions for the pitch of the helix and magnetization of ferrocholesteric depending on the anchoring energy, field influence parameter, strength and orientation angle of the magnetic field, flow gradient and reactive parameter. It is shown that the shear flow is able to magnetize a ferrocholesteric liquid crystal. An increase in the field influence parameter or gradient of the shear flow velocity leads to a decrease in the critical fields of the ferrocholesteric-ferronematic transition. (paper)