Observation of a phase transition within the domain walls of ferromagnetic Co3Sn2S2

Changmin Lee; Praveen Vir; Kaustuv Manna; Chandra Shekhar; J E Moore; M A Kastner; Claudia Felser; Joseph Orenstein

doi:10.1038/s41467-022-30460-y

Observation of a phase transition within the domain walls of ferromagnetic Co₃Sn₂S₂

Nat Commun. 2022 May 30;13(1):3000. doi: 10.1038/s41467-022-30460-y.

Authors

Changmin Lee¹, Praveen Vir², Kaustuv Manna^{2

3}, Chandra Shekhar², J E Moore^{1

4}, M A Kastner^{5

6

7}, Claudia Felser², Joseph Orenstein^{8

9}

Affiliations

¹ Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
² Max Planck Institute for Chemical Physics of Solids, Dresden, Germany.
³ Department of Physics, Indian Institute of Technology Delhi, New Delhi, India.
⁴ Department of Physics, University of California at Berkeley, Berkeley, CA, USA.
⁵ Department of Physics, Stanford University, Palo Alto, CA, USA.
⁶ Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
⁷ Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA.
⁸ Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. jworenstein@lbl.gov.
⁹ Department of Physics, University of California at Berkeley, Berkeley, CA, USA. jworenstein@lbl.gov.

Abstract

The ferromagnetic phase of Co₃Sn₂S₂ is widely considered to be a topological Weyl semimetal, with evidence for momentum-space monopoles of Berry curvature from transport and spectroscopic probes. As the bandstructure is highly sensitive to the magnetic order, attention has focused on anomalies in magnetization, susceptibility and transport measurements that are seen well below the Curie temperature, leading to speculation that a "hidden" phase coexists with ferromagnetism. Here we report spatially-resolved measurements by Kerr effect microscopy that identify this phase. We find that the anomalies coincide with a deep minimum in domain wall (DW) mobility, indicating a crossover between two regimes of DW propagation. We demonstrate that this crossover is a manifestation of a 2D phase transition that occurs within the DW, in which the magnetization texture changes from continuous rotation to unidirectional variation. We propose that the existence of this 2D transition deep within the ferromagnetic state of the bulk is a consequence of a giant quality factor for magnetocrystalline anisotropy unique to this compound. This work broadens the horizon of the conventional binary classification of DWs into Bloch and Néel walls, and suggests new strategies for manipulation of domain walls and their role in electron and spin transport.

Abstract

Grants and funding