Title: Fan-type spin structure in uni-axial chiral magnets,
Abstract: We investigate the spin structure of a uni-axial chiral magnet near the
transition temperatures in low fields perpendicular to the helical axis. We
find a fan-type modulation structure where the clockwise and counterclockwise
windings appear alternatively along the propagation direction of the modulation
structure. This structure is often realized in a Yoshimori-type (non-chiral)
helimagnet but it is rarely realized in a chiral helimagnet. To discuss
underlying physics of this structure, we reconsider the phase diagram (phase
boundary and crossover lines) through the free energy and asymptotic behaviors
of isolated solitons. The fan structure appears slightly below the phase
boundary of the continuous transition of instability-type. In this region,
there are no solutions containing any types of isolated solitons to the mean
field equations.