Kinetic small angle neutron scattering of the Skyrmion lattice in MnSi

TL;DR

This study uses kinetic small angle neutron scattering to investigate the elasticity, relaxation, and pinning of the skyrmion lattice in MnSi, revealing its dynamic response to magnetic field tilting and temperature variations.

Contribution

It introduces kinetic small angle neutron scattering as a novel method to probe skyrmion lattice dynamics and pinning effects with high temporal resolution.

Findings

Skyrmion lattice begins to follow magnetic field tilting above 0.4° at 325 Hz.

The angular velocity of tilting correlates with critical charge carrier velocity for unpinning.

Skyrmion stiffness varies significantly with temperature, affecting skyrmion motion.

Abstract

We report a kinetic small angle neutron scattering study of the skyrmion lattice (SL) in MnSi. Induced by an oscillatory tilting of the magnetic field direction, the elasticity and relaxation of the SL along the magnetic field direction have been measured with microsecond resolution. For the excitation frequency of 325 Hz the SL begins to track the tilting motion of the applied magnetic field under tilting angles exceeding $\alpha_c$ > 0.4{\deg}. Empirically the associated angular velocity of the tilting connects quantitatively with the critical charge carrier velocity of approx. 0.1mm/s under current driven spin transfer torques, for which the SL unpins. In addition, a pronounced temperature dependence of the skyrmion motion is attributed to the variation of the skyrmion stiffness. Taken together our study highlights the power of kinetic small angle neutron scattering as a new experimental tool to explore, in a rather general manner, the elasticity and impurity pinning of magnetic textures across a wide parameter space without parasitic signal interferences due to ohmic heating or Oersted magnetic fields.