Colossal topological Hall effect at the transition between isolated and lattice-phase interfacial skyrmions

M Raju,I Mertig,I V Rozhansky,A P Petrović,B Göbel,E Şaşıoğlu,N K Duong,O M Auslaender,A Yagil,C Panagopoulos,K S Denisov

doi:10.1038/s41467-021-22976-6

Abstract

The topological Hall effect is used extensively to study chiral spin textures in various materials. However, the factors controlling its magnitude in technologically-relevant thin films remain uncertain. Using variable-temperature magnetotransport and real-space magnetic imaging in a series of Ir/Fe/Co/Pt heterostructures, here we report that the chiral spin fluctuations at the phase boundary between isolated skyrmions and a disordered skyrmion lattice result in a power-law enhancement of the topological Hall resistivity by up to three orders of magnitude. Our work reveals the dominant role of skyrmion stability and configuration in determining the magnitude of the topological Hall effect.

Highlights

The topological Hall effect is used extensively to study chiral spin textures in various materials
magnetic force microscopy (MFM) images acquired at H maximizing ρTHE(H) display spin configurations ranging from isolated skyrmions (Fig. 1a–c) to dense, disordered skyrmion lattices (Fig. 1d–g)
In chiral magnetic films, the transformation of a polarized FM phase into an array of isolated skyrmions and a skyrmion lattice occurs via a nucleation-type secondorder phase transition[22,23,24]

Summary

Introduction

The topological Hall effect is used extensively to study chiral spin textures in various materials. R0), Beff ≡ nsk ⋅ Φ0 is the emergent field associated with a given skyrmion density nsk, and Φ0 = h/e is the magnetic flux quantum, with h Planck’s constant and −e the electron charge This phenomenon is distinct from the classical and anomalous Hall effects, which are proportional to the applied magnetic field H and magnetization M(H), respectively[7]. Using Eq (1) and our experimentally-determined ρTHE, one can estimate nsk from an electrical transport measurement as: nskðTHEÞ 1⁄4 jρTHEj Ä jðP Á R0 Á Φ0Þj: ð2Þ nsk may be measured directly using real-space imaging techniques such as magnetic force microscopy (MFM)[9,10,11], magnetic transmission X-ray microscopy[4,5], or Lorentz transmission electron microscopy[12] Comparing these transport and imaging approaches can yield evidence for adiabatic transport if nsk(THE) ≈ nsk(MFM)[6,7,8], non-adiabaticity if nsk(THE) < nsk(MFM)[13,14], or alternatively reveal enhanced transverse scattering mechanisms if nsk(THE) > nsk(MFM)[13,15,16,17]

Methods

Results

Conclusion