Kinetic small angle neutron scattering of the skyrmion lattice in MnSi

S Mühlbauer,J Kindervater,C Pfleiderer,T Adams,A Bauer,U Keiderling

doi:10.1088/1367-2630/18/7/075017

Abstract

We report a kinetic small angle neutron scattering (SANS) 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 the SL begins to track the tilting motion of the applied magnetic field under tilting angles exceeding . Empirically the associated angular velocity of the tilting connects quantitatively with the critical charge carrier velocity of 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 SANS 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.

Highlights

The observation of an unusual rotation of the neutron diffraction pattern of the so-called A-phase in MnSi under an electric current applied perpendicular to the magnetic field stabilising the A-phase [1, 2], resulted in the first identification of a skyrmion lattice as a new form of magnetic order [3, 4]
Data were recorded in the static mode and the in time-resolved TIme resolved SANS Experiments’ (TISANE) mode driven by the oscillating magnetic field orientation
Before we turn to the time resolved data, it proves to be helpful to summarise data recorded in the standard small angle neutron scattering (SANS) mode without oscillating field component

Summary

Introduction

The observation of an unusual rotation of the neutron diffraction pattern of the so-called A-phase in MnSi under an electric current applied perpendicular to the magnetic field stabilising the A-phase [1, 2], resulted in the first identification of a skyrmion lattice as a new form of magnetic order [3, 4]. A series of comprehensive studies have established beyond doubt the early conjecture, that the skyrmion lattice in cubic chiral magnets is generic and stabilised by the effects of thermal fluctuations [7, 8, 9, 10, 11, 12]. Careful measurements avoiding inhomogeneities of the applied magnetic field due to the effects of demagnetisation reveal, that the skyrmion lattice phase is ordered exceptionally well with resolution-limited magnetic coherence length exceeding at least several 10−6 m [14]

Methods

Results

Discussion

Conclusion