The search for new spin-liquid materials – synthesis of kagome and pyrochlore fluoride magnets

• Thesis title in Czech: Hledání nových spinových kapalin - syntéza kagomé a pyrochlór-fluoridových magnetů
• Thesis title in English: The search for new spin-liquid materials – synthesis of kagome and pyrochlore fluoride magnets
• Key words: frustrovaný magnetizmus|kvantová spinová kapalina|pyrochlor|kagome|antiferomagnet
• English key words: Magnetism|Synthesis|Quantum spin liquid
• Academic year of topic announcement: 2023/2024
• Thesis type: rigorosum thesis
• Thesis language: angličtina
• Department: Department of Condensed Matter Physics (32-KFKL)
• Supervisor: Ross Harvey Colman, Dr.
• Author: hidden - assigned and confirmed by the Study Dept.
• Date of registration: 05.01.2024
• Date of assignment: 05.01.2024
• Confirmed by Study dept. on: 05.01.2024
• Date and time of defence: 28.02.2024 00:00
• Date of electronic submission: 05.01.2024
• Date of submission of printed version: 05.01.2024
• Date of proceeded defence: 28.02.2024

Guidelines

1. Prepare samples
2. Characterise sample by magnetometry and X-ray diffraction
3. Write a report

References

[1] Balents, L. Nature (2010) 464, 199.
[2] Clark, B. Physics (2017) 10, 33 [physics.aps.org/articles/v10/33].
[3] Sanders, M. B. et al. J. Mater. Chem. C (2016) 4, 541.
[4] Sanders, M. B. et al. Phys. Status Solidi B (2016) 253, 2056.
[5] Scheie, A. et al. Rhys. Rev. B (2016) 93, 180407(R).
[6] Fu, W.T. et al. J. Solid State Chem. (2014) 213, 165.
[7] Li, K. et al. J. Solid State Chem. (2014) 217, 80.
[8] Mumme, W. G. Am. Miner. (2010) 95, 736.
[9] R. Hansler and W. Rudorff, Z. Naturforsch. B (1970) 25, 1306.
[10] J.W. Krizan, R.J. Cava, Phys. Rev. B - Condens. Matter Mater. Phys. 89 (2014) 1–5. doi:10.1103/PhysRevB.89.214401.
[11] J.W. Krizan, R.J. Cava, Phys. Rev. B. 92 (2015) 014406. doi:10.1103/PhysRevB.92.014406.

Preliminary scope of work

The study of emergent phenomena considers how a simple set of interactions between microscopic components in a system can lead to unexpected macroscopic properties, such as consciousness arising from interactions between neurones or complex weather systems arising from interactions between air molecules. Geometrically frustrated magnets are an ideal place to study emergent phenomena due to the relevant simplicity of magnetic interactions [1]. Geometric frustration, where the lattice geometry prevents the simultaneous satisfaction of all the magnetic interactions, is one way of creating unconventional magnetic ground-states and a can provide convenient models for studying emergent phenomena. Antiferromagnetically coupled magnetic ions on a kagome lattice, a lattice built of vertex sharing triangles, is considered one of the most highly frustrated types of arrangements and there have been long debates about the nature of the ground-state that should emerge on such a lattice, lasting for over a decade [2].
One key point that has perpetuated this discussion is the lack of good model materials to investigate such a situation experimentally. Some models exist but every model material has associated problems that prevent us reaching a definitive answer to the question.
One method of creating a kagome lattice is through the ordered dilution of a pyrochlore lattice, made up of vertex sharing tetrahedra. This has been seen in several rare-earth materials recently with the general formula RE3M2Sb3O14 (RE = rare earth ion, M = Zn, Mg, Mn or Co) [3-7] and is seen in the mineral with formula CaNa3AlMg3F14 [8]. Due to the chemical similarity between Mg2+ (diamagnetic) and Cu2+ (magnetically active, s=1/2 ion), and their similar ionic radii 0.72 vs. 0.73 Å3, respectively, this project will aim to synthesise a new kagome material with formula CaNa3AlCu3F14, through solid state synthesis techniques from fluoride salt precursors. Once synthesised, the magnetic and electrical properties will be investigated and other chemical substitutions can be attempted. If the calcium containing materials are not possible to prepare, the cadmium-copper pyrochlore fluorides NaCdCu2F7 (previously reported[8]) and proposed kagome fluoride CdNa3Cu3AlF14 will be the targets. Alternative pyrochlore cadmium fluorides with alternative transition metals may also prove interesting for study, similar to recent reports on NaCaCo2F7, NaCa [10,11].

Preliminary scope of work in English

The study of emergent phenomena considers how a simple set of interactions between microscopic components in a system can lead to unexpected macroscopic properties, such as consciousness arising from interactions between neurones or complex weather systems arising from interactions between air molecules. Geometrically frustrated magnets are an ideal place to study emergent phenomena due to the relevant simplicity of magnetic interactions [1]. Geometric frustration, where the lattice geometry prevents the simultaneous satisfaction of all the magnetic interactions, is one way of creating unconventional magnetic ground-states and a can provide convenient models for studying emergent phenomena. Antiferromagnetically coupled magnetic ions on a kagome lattice, a lattice built of vertex sharing triangles, is considered one of the most highly frustrated types of arrangements and there have been long debates about the nature of the ground-state that should emerge on such a lattice, lasting for over a decade [2].
One key point that has perpetuated this discussion is the lack of good model materials to investigate such a situation experimentally. Some models exist but every model material has associated problems that prevent us reaching a definitive answer to the question.
One method of creating a kagome lattice is through the ordered dilution of a pyrochlore lattice, made up of vertex sharing tetrahedra. This has been seen in several rare-earth materials recently with the general formula RE3M2Sb3O14 (RE = rare earth ion, M = Zn, Mg, Mn or Co) [3-7] and is seen in the mineral with formula CaNa3AlMg3F14 [8]. Due to the chemical similarity between Mg2+ (diamagnetic) and Cu2+ (magnetically active, s=1/2 ion), and their similar ionic radii 0.72 vs. 0.73 Å3, respectively, this project will aim to synthesise a new kagome material with formula CaNa3AlCu3F14, through solid state synthesis techniques from fluoride salt precursors. Once synthesised, the magnetic and electrical properties will be investigated and other chemical substitutions can be attempted. If the calcium containing materials are not possible to prepare, the cadmium-copper pyrochlore fluorides NaCdCu2F7 (previously reported[8]) and proposed kagome fluoride CdNa3Cu3AlF14 will be the targets. Alternative pyrochlore cadmium fluorides with alternative transition metals may also prove interesting for study, similar to recent reports on NaCaCo2F7 and NaCaNi2F7 [10,11].