Phase diagram of the chiral magnet Cr1/3NbS2 in a magnetic field

We construct the phase diagram of the chiral magnet Cr1/3NbS2 in a dc magnetic field (Hdc) using ac magnetic susceptibility measurements. At Hdc=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 (M3ω) and a first-order harmonic component (M1ω). By applying Hdc perpendicular to the c axis, the HM state is transformed to the chiral soliton lattice (CSL) state, which is a superlattice tuned by Hdc. The above giant M3ω is markedly suppressed at small Hdc. 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 M1ω. 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 M3ω and large out-of-phase M1ω as well as in-phase M1ω. The transition between the FMM and PM states also yields a linear magnetic response, like the CSL-1-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.