Phase diagram of the chiral magnet Cr 1 / 3 NbS 2 in a magnetic field

We construct the phase diagram of the chiral magnet ${\mathrm{Cr}}_{1/3}{\mathrm{NbS}}_{2}$ in a dc magnetic field $({H}_{\mathrm{dc}})$ using ac magnetic susceptibility measurements. At ${H}_{\mathrm{dc}}=0$, the ac response at the transition from the helical magnetic (HM) state to the paramagnetic (PM) state consists of a giant third-order harmonic component $({M}_{3\ensuremath{\omega}})$ and a first-order harmonic component $({M}_{1\ensuremath{\omega}})$. By applying ${H}_{\mathrm{dc}}$ perpendicular to the $c$ axis, the HM state is transformed to the chiral soliton lattice (CSL) state, which is a superlattice tuned by ${H}_{\mathrm{dc}}$. The above giant ${M}_{3\ensuremath{\omega}}$ is markedly suppressed at small ${H}_{\mathrm{dc}}$. The CSL state is found to consist of CSL-1, with dominant helical texture and a poor ferromagnetic array, and CSL-2, with a large ferromagnetic array. The transition between CSL-1 and the PM state causes a linear magnetic response, the dominant component of which is the in-phase ${M}_{1\ensuremath{\omega}}$. With increasing temperature, CSL-2 is transformed into the forced ferromagnetic (FFM) state, and ultimately the PM state is reached. The transition between CSL-2 and the FFM state consists of a large ${M}_{3\ensuremath{\omega}}$ and large out-of-phase ${M}_{1\ensuremath{\omega}}$ as well as in-phase ${M}_{1\ensuremath{\omega}}$. The transition between the FMM and PM states also yields a linear magnetic response, like the CSL-1\char21{}PM-state transition. Five typical magnetic dynamics in the transitions among the HM state, CSL-1, CSL-2, FFM state, and PM state were identified according to the equivalent dynamical motion equation of a nonlinear spring model.