Transport Properties of Weyl Semimetal Mn3Sn
Date
Authors
Type
Examensarbete för masterexamen
Programme
Model builders
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The antiferromagneticWeyl semimetalMn3Sn has recently been of great interest because
of exotic transport behaviors it exhibits at room temperature, such as Planar
Hall Effect (PHE), large AnomalousHall Effect (AHE) and negativemagnetoresistance
(MR). These exotic behaviors, rarely found in antiferromagnets, have potential to be
utilized in future spintronics devices.
Mn3Sn compounds need to be stabilized in excess of Mn, which means that the actual
composition is Mn3+δSn for δ ∈ [0.05,0.3]. Reports of the different exotic effects
and other properties are therefore often attained from samples with varyingMn concentrations.
In this thesis, we present extensive measurements of both magnetic and
electronic transport properties of Mn3.13Sn for a wide temperature range, with the
goal tomap all the transport properties ofMn3Sn for a single compound.
All measurements have been conducted at the Jülich Centre for Neutron Science
(JCNS) using the Quantum Design Physical Property Measurement System (PPMS)
and Magnetic Property Measurement System (MPMS). We are able to identify three
transition temperatures ofMn3.13Sn; Tf = 45K, Tt = 245K and TN = 410K. Below Tf ,
we confirm a weakly ferromagnetic phase with magnetic easy direction [0001]. AC
susceptibility measurements also reveal a slight glassiness in this phase, consistent
with the previous reports. Furthermore, MR measurements display competingWeak
Localization and Anti-weak Localization effects belowTf . TN is identified as the Néel
temperature above which the antiferromagnetic structure is destroyed.
Above Tt , we clearly observe PHE, AHE as well as negative MR. Between Tf < T < Tt
the Mn moments order in a spiral structure. In this temperature range both PHE,
AHE and negative MR vanishes, consistent with earlier reports. We identify a six-fold
anisotropy in magnetization confirming a triangular antiferromagnetic spin structure
above Tt and observe the lowest-energy direction in the triangular configuration
to be [11¯20]. This phase is also weakly ferromagnetic, and we find the easy direction
to be in [11¯20] direction for low external magnetic field which shifts to [0001] at a
high magnetic field. To further characterize the change in lowest-energy direction
we suggest a more detailed study.
Description
Keywords
Weyl Semimetal, Topological Materials, Planar Hall effect, Anomalous Hall effect, Mn3Sn, Weak Localization, Weak Anti-Localization, Chiral Anomaly