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Structural and magnetic investigations of chiral magnets
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Hall, Amelia Elisabeth (2022) Structural and magnetic investigations of chiral magnets. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3883167
Abstract
Investigations of the magnetic structures and phase diagrams of chiral magnetic materials has led to the discovery of topological magnetic phenomena such as skyrmions and the chiral soliton lattice, which are of interest for spintronics device applications. In this thesis, the structural and magnetic properties of several chiral magnetic materials are explored, focusing on the intercalated transition metal dichalcogenides and the frustrated antiferromagnetic Mn3XY (X =Rh,Ir, Y =Si,Ge) families of materials.
Firstly, the magnetic structure of V1=3NbS2 is studied and found to display behaviour consistent with a canted antiferromagnet. Two propagation vectors are required to index all the magnetic Bragg peaks present in powder neutron di_raction data; the k0 = (0,0,0) propagation vector is associated with an in-plane A-type antiferromagnetic ordering, while the k1=3 = (0,0,1/3) magnetic propagation vector can be associated with an up-down-down con_guration of moments along the c axis. A ferromagnetic component too small to be resolved in these measurements is expected from magnetisation data.
This thesis goes on to describe a detailed structural and magnetic investigation to compare single crystals of Mn1=3NbS2, Cr1=3NbS2, and Cr1=3TaS2. Lorentz transmission electron microscopy measurements show the presence of helimagnetic ordering in Cr1=3NbS2 below TC = 111 K, while there is no evidence that Mn1=3NbS2 exhibits helimagnetic ordering below TC = 45 K. An analogue is drawn between the magnetic phase diagrams of Cr1=3NbS2, Cr1=3TaS2, and Mn1=3NbS2, constructed from ac susceptibility measurements.
Finally, this thesis describes an investigation into Mn3IrSi, Mn3RhGe, and Mn3RhSi. A single crystal of Mn3RhSi has been successfully grown and its magnetic properties investigated with dc susceptibility measurements to show a magnetic transition at 228 K. Powder neutron di_raction investigations into polycrystalline Mn3IrSi and Mn3RhGe reveal a three-dimensional frustrated antiferromagnetic ground state for both materials, while Mn3RhGe exhibits an incommensurate helical magnetic phase at 200 K.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QC Physics | ||||
Library of Congress Subject Headings (LCSH): | Chirality, Magnetic materials, Chalcogenides -- Magnetic properties, Ferromagnetic materials, Skyrme model | ||||
Official Date: | July 2022 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Balakrishnan, Geetha | ||||
Sponsors: | Engineering and Physical Sciences Research Council | ||||
Format of File: | |||||
Extent: | xxxvi, 161 pages : colour illustrations, colour charts | ||||
Language: | eng |
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