Non-collinear spin textures have attracted significant attention due to their topological nature, emergent electromagnetic properties, and potential spintronic and magnonic device applications. This book explores the physical properties of distinct spin textures in D2d compounds. The main goals of the work are (a) discovering new spin textures in D2d Heusler compounds and studying their detailed properties to enrich the field of non-collinear magnetism (b) optimizing the nano-track geometry and generating isolated and single chains of nano-objects that will establish new hallmarks for technological applications (c) studying the stability of spin textures with magnetic fields and temperatures and finding a way to observe the striking behavior of spin textures near the specimen edges. The first few chapters provide a brief overview of spin textures such as Bloch and Néel skyrmions. In the experimental methods section, the author shows how to identify the single-crystalline grains of a polycrystalline sample, how to make single-crystalline thin specimens and nano-tracks, and then provides explicit descriptions of different imaging techniques performed on a transmission electron microscope. This part will be valuable for beginners wishing to conduct research in experimental nano-magnetism and transmission electron microscope imaging. The core results of the book are presented in four chapters, describing the discovery of several new and unanticipated spin textures, namely square-shaped antiskyrmions, elliptical Bloch skyrmions, fractional antiskyrmions, fractional Bloch skyrmions and elongated (anti)skyrmions in a single D2d Heusler compound. It is shown that these textures can be understood by a combination of dipole-dipole interactions and a chiral vector exchange that makes it possible to stabilize various spin textures even in the same compound. The D2d compounds are the first non-centrosymmetric systems shown to host several co-existing non-collinear spin textures.
Author(s): Jagannath Jena
Series: Springer Theses
Publisher: Springer
Year: 2022
Language: English
Pages: 146
City: Cham
Supervisor’s Foreword
Abstract
Publications related to this thesis
Acknowledgements
Contents
Abbreviations
1 Introduction
References
2 Magnetic Skyrmions
2.1 Non-collinear Magnetism
2.2 Magnetic Skyrmions
2.3 Magnetic Antiskyrmions
2.4 Topological Definition of Skyrmions
2.5 Energy Terms for Stabilizing Skyrmions
2.5.1 Exchange Interaction
2.5.2 Zeeman Interaction and Anisotropies
2.5.3 Dzyaloshinskii-Moriya Interaction
2.5.4 Dipole–Dipole Interactions
2.6 Towards Application of Skyrmions
2.7 Stabilization of Different Spin Textures in Single Material System
2.8 Summary
References
3 Experimental Methods
3.1 Magnetization Measurement
3.2 Scanning Electron Microscopy and Electron Backscatter Diffraction
3.3 Focused Ion Beam
3.4 Transmission Electron Microscopy
3.5 Electron Diffraction
3.6 Lorentz Transmission Electron Microscopy
3.7 High-Resolution and Scanning Transmission Electron Microscopy
3.8 Summary
References
4 Elliptical Bloch Skyrmions and Antiskyrmions in a D2d Inverse Heusler Compound
4.1 Introduction
4.2 Methods
4.2.1 Experimental Details
4.2.2 Micromagnetic Simulations
4.3 Results and Discussion
4.3.1 Round and Square Antiskyrmions
4.3.2 Elliptical Bloch Skyrmions
4.3.3 Enhanced Stability of Elliptical Bloch Skyrmions
4.3.4 Elliptical Bloch Skyrmion Chiral Twins
4.3.5 Switching Between Round and Square Antiskyrmions
4.3.6 Simultaneous Existence of Elliptical Skyrmions and Antiskyrmions
4.3.7 Magnetic Phase Diagram
4.4 Summary
References
5 Evolution and Competition Between Chiral Spin Textures in Nano-stripes
5.1 Introduction
5.2 Methods
5.2.1 Experimental Details
5.2.2 Micromagnetic Simulations
5.3 Result and Discussion
5.3.1 Nano-stripes Along Different Crystallographic Directions
5.3.2 Helices and Antiskyrmions in [010] Oriented Nano-stripes
5.3.3 Difference Between Helices and Other Domains in D2d System
5.3.4 Antiskyrmion Chains in Differently Oriented Nano-stripes
5.3.5 Co-existence of Elliptical Skyrmions and Antiskyrmions at Room Temperature
5.4 Summary
References
6 Stability, Collapse Dynamics and Fractional Form of Antiskyrmions and Elliptical Bloch Skyrmions
6.1 Introduction
6.2 Experimental Details
6.3 Results and Discussion
6.3.1 Metastability of Square Antiskyrmions
6.3.2 Collapse Dynamics of Antiskyrmions and Elliptical Skyrmions
6.3.3 Fractional Elliptical Bloch Skyrmions and Antiskyrmions
6.3.4 In-Plane Field Dependent Metastability of Spin Textures
6.3.5 Evaluation of Spin Textures from the Helical State
6.3.6 Stability of Elliptical Bloch Skyrmions Against Heating
6.4 Summary
References
7 Observation of Antiskyrmions and Bloch Skyrmions in a Low Moment Ferrimagnetic Heusler Compound
7.1 Introduction
7.2 Experimental Methods
7.2.1 Bulk Polycrystalline Synthesis
7.2.2 Powder XRD, EDXS, and EBSD
7.2.3 Magnetization Measurements
7.2.4 Microscopy Characterizations
7.3 Results and Discussion
7.3.1 Magnetic Antiskyrmions in Mn2Rh0.95Ir0.05Sn
7.3.2 Field Driven Formation of Antiskyrmions
7.3.3 Helical Periods of Mn2Rh0.95Ir0.05Sn and Mn1.4Pt0.9Pd0.1Sn
7.3.4 Bloch Skyrmions in Mn2Rh0.95Ir0.05Sn
7.3.5 Field Driven Formation of Bloch Skyrmions
7.3.6 Stability of Bloch Skyrmions Against Heating
7.4 Summary
References
8 Conclusion and Outlook
8.1 Conclusion
8.2 Future Perspectives
References
Appendix A Supplementary Figure for Elliptical Bloch Skyrmions and Antiskyrmions in a D2d Inverse Heusler Compound
A.1 Elliptical Bloch Skyrmions at 150 and 250 K
Appendix B Supplementary Figures for Evolution and Competition Between Chiral Spin Textures in Nano-stripes
B.1 Effect of Field on Helix and Magnetic Domain
B.2 Single, Double and Elongated Antiskyrmions at 490 nm Width Stripe
Appendix C Supplementary Figures for Stability, Collapse Dynamics and Fractional Form of Antiskyrmions and Elliptical Bloch Skyrmions
C.1 Transition Between the Antiskyrmion and Helices
C.2 Effect of In-Plane Field Component on Antiskyrmion
C.3 Elliptical Bloch Skyrmion in the Field Increasing Mode
Curriculum Vitae
