Frustrated magnetic fluorides

• Název práce v češtině: Frustrated magnetic fluorides
• Název v anglickém jazyce: Frustrated magnetic fluorides
• Klíčová slova: Frustrated magnetism|Pyrochlore|Kagome|Fluoride metal transition|Spin-liquid|Spin-glass|Magnetometry|Diffraction|Heat capacity
• Klíčová slova anglicky: Frustrated magnetism|Pyrochlore|Kagome|Fluoride metal transition|Spin-liquid|Spin-glass|Magnetometry|Diffraction|Heat capacity
• Akademický rok vypsání: 2022/2023
• Typ práce: disertační práce
• Jazyk práce: čeština
• Ústav: Katedra fyziky kondenzovaných látek (32-KFKL)
• Vedoucí / školitel: Ross Harvey Colman, Dr.
• Řešitel: skrytý - zadáno a potvrzeno stud. odd.
• Datum přihlášení: 02.08.2022
• Datum zadání: 02.08.2022
• Datum potvrzení stud. oddělením: 27.09.2022

Zásady pro vypracování

Frustrated magnetic materials have been extensively studied in recent decades due to the plethora of exotic ground-state magnetic and electronic properties that have been both predicted and observed [1]. The relatively simple interactions between ions often leads to unexpected emergent properties. Transition metal and rare-earth oxides form the most widely studied groups, due to their abundance and simplicity. The rare-earth pyrochlore oxides, with general formula A2B2O7, have provided a wealth of interesting physics due to their 3-dimensional frustrated lattice, coupled with a broad range of interchangeable magnetic rare-earth A-site ions [2]. Recently, several compounds that form Kagome lattices have also been prepared through selective substitution of the pyrochlore lattice [3,4].
When fluoride ions link transition metal ions, they can mediate the magnetic super-exchange with a similar strength to oxide ions but despite this the magnetic transition metal fluorides remain a relatively understudied group when compared to the oxides. In recent years a number of transition metal fluoride compounds with a pyrochlore structure have been identified [5–7], and just like the rare-earth pyrochlores there is the potential for a wide variety of possible A-site and B-site substitutions that could lead to new and un-studied members. These compounds hold the potential for observing unconventional ground-state physics at higher temperature than their rare-earth oxide counterparts due to the more extended nature of the 3d-orbitals compared to the 4f-orbitals, leading to stronger magnetic exchange interactions. Like the rare-earth oxides, these compounds also hold the possibility of site-selective substitution to potentially prepare new transition metal Kagome fluorides [8].
Already, a number of exotic ground-state properties have been observed, with the frustration of the pyrochlore lattice leading to continued spin-dynamics below the nominal glass transition [9–11].
This project will focus on extending the, currently limited, list of pyrochlore fluoride compounds through transition metal and A-site substitution. The selection of potential targets will be guided by the well-developed ion-size compatibility and stability rules governing the pyrochlore structure [12]. The magnetic, electronic and physical properties of all new compounds will be studied by both in-house and external large-scale facilities experiments. If applicable, the project will extend to the preparation of Kagome systems through the dilution of the transition metal fluoride pyrochlore lattice.
The student will gain knowledge and experience in solid-state synthesis and crystal growth, as well as working under inert atmospheres. Characterisation tools that the student will use include several instruments of the Materials Growth and Measurement Laboratory (MGML), such as the Quantum Design Magnetic Properties Measurement System (MPMS), and Physical Properties Measurement System (PPMS), as well as structural characterisation and orientation tools such as the departmental diffractometers. Large-scale facility experiments may include synchrotron X-ray, neutron, and muon investigations of the materials. Additionally, the student may have the opportunity to perform nuclear magnetic resonance (NMR) investigations of the prepared samples with collaborators in external laboratories.
The student will also be expected to present these results to the scientific community, both through the preparation of published research articles, as well as through presentation at conferences.

Seznam odborné literatury

[1] L. Balents, Spin Liquids in Frustrated Magnets, Nature 464, 199 (2010).
[2] J. S. Gardner, M. J. P. Gingras, and J. E. Greedan, Magnetic Pyrochlore Oxides, Rev. Mod. Phys. 82, 53 (2010).
[3] A. Scheie, M. Sanders, J. Krizan, Y. Qiu, R. J. Cava, and C. Broholm, Effective Spin- 12 Scalar Chiral Order on Kagome Lattices in Nd3Sb3Mg2 O14, Phys. Rev. B 93, 180407 (2016).
[4] M. B. Sanders, J. W. Krizan, and R. J. Cava, A New Family of Pyrochlore Derivatives with Rare Earth Ions on a 2D Kagome Lattice We Report the Synthesis and Crystal Structures of Compounds of the Type RE 3 Sb 3 Zn 2 O 14 (La 3 Sb 3 Zn 2 O 14 , Pr 3 Sb 3 Zn 2 O 14 , Nd 3 Sb 3 Zn 2 O 14 , Sm 3 Sb 3 Zn , J. Mater. Chem. C 4, 541 (2016).
[5] M. B. Sanders, J. W. Krizan, K. W. Plumb, T. M. McQueen, and R. J. Cava, NaSrMn2F7, NaCaFe2F7, and NaSrFe2F7: Novel Single Crystal Pyrochlore Antiferromagnets, J. Phys. Condens. Matter 29, 045801 (2017).
[6] J. W. Krizan and R. J. Cava, NaCaN I2 F7: A Frustrated High-Temperature Pyrochlore Antiferromagnet with S=1 N I2+, Phys. Rev. B 92, 014406 (2015).
[7] J. W. Krizan and R. J. Cava, NaSrCo 2 F 7 , a Co 2+ Pyrochlore Antiferromagnet, J. Phys. Condens. Matter 27, 296002 (2015).
[8] W. G. Mumme, I. E. Grey, W. D. Birch, A. Pring, C. Bougerol, and N. C. Wilson, Coulsellite, CaNa3AlMg3F14, a Rhombohedral Pyrochlore with 1:3 Ordering in Both A and B Sites, from the Cleveland Mine, Tasmania, Australia, Am. Mineral. 95, 736 (2010).
[9] K. W. Plumb, H. J. Changlani, A. Scheie, S. Zhang, J. W. Krizan, J. A. Rodriguez-Rivera, Y. Qiu, B. Winn, R. J. Cava, and C. L. Broholm, Continuum of Quantum Fluctuations in a Three-Dimensional S = 1 Heisenberg Magnet, Nat. Phys. 15, 54 (2019).
[10] Y. Cai, M. N. Wilson, A. M. Hallas, L. Liu, B. A. Frandsen, S. R. Dunsiger, J. W. Krizan, R. J. Cava, O. Rubel, Y. J. Uemura, and G. M. Luke, ΜsR Study of Spin Freezing and Persistent Spin Dynamics in NaCaNi2F7, J. Phys. Condens. Matter 30, (2018).
[11] R. Sarkar, J. W. Krizan, F. Brückner, E. C. Andrade, S. Rachel, M. Vojta, R. J. Cava, and H. H. Klauss, Spin Freezing in the Disordered Pyrochlore Magnet NaCaCo2 F7: NMR Studies and Monte Carlo Simulations, Phys. Rev. B 96, 1 (2017).
[12] Z. Song and Q. Liu, Tolerance Factor, Phase Stability and Order-Disorder of the Pyrochlore Structure, Inorg. Chem. Front. 7, 1583 (2020).