Nonequilibrium spin dynamics in the chiral soliton lattice host YbNi3Al9

The uniaxial chiral magnetic material YbNi 3 Al 9 is proposed as a host for a chiral soliton lattice (CSL). In this study, we thoroughly investigate the spin dynamics in YbNi 3 Al 9 single crystals using magnetization ( M )-relaxation and electron spin resonance (ESR) techniques. The M -relaxation analysis clearly reveals characteristics of a nonequilibrium CSL in YbNi 3 Al 9 . A prolonged relaxation is observed in the highly-nonlinear-CSL state, indicating nonequilibrium spin dynamics during the annihilation or nucleation of chiral magnetic solitons, consistent with the unfrustrated magnetic cluster model. The ESR study shows significant microwave responses when the magnetic field is applied perpendicular to the c -axis ( H ⊥ c ), while a weak response is observed when the field is aligned with the c -axis ( H / / c ). Two resonance lines are identified for H ⊥ c . The resonance signal at lower fields is attributed to the Goldstone excitation of chiral magnetic solitons, while the signal at higher fields is associated with ferromagnetic resonance. These findings enhance our understanding of the nonequilibrium spin dynamics of the CSL in YbNi 3 Al 9 single crystals and are beneficial for the application of chiral magnetic solitons in spintronics. Figure: The M -relaxation of YbNi 3 Al 9 single crystal. (a)-(c) Time evolution of M - relaxation at 2 K, 3 K, 4 K, respectively. The initial fields (H it ) were set at 1000 Oe and at loop areas. (d) The enlarged M -relaxation curve at 3 K (the arrows point out the annihilation and nucleation of chiral magnetic solitons). (e) The experimental and fitted curves of M -relaxation for solitons nucleation at different temperatures. (f) Magnified magnetic loops of dc M ( H ) , where solid circles indicate H -ascending, open circles indicate H -descending. The arrows indicate Hit at which the M -relaxation was conducted in panels (a)-(c). • A prolonged relaxation is observed in nonequilibrium CSL state of YbNi 3 Al 9 . • The ESR study shows significant microwave responses when H ⊥ c and H//c. • The resonance signal at lower fields is attributed to the Goldstone excitation of chiral magnetic solitons.