Kinetic small angle neutron scattering of the skyrmion lattice in MnSi

Abstract

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