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Title:Rapid materials discovery of ternary transition metal chalcogenides
Author(s):Bhutani, Ankita
Director of Research:Shoemaker, Daniel P.
Doctoral Committee Chair(s):Shoemaker, Daniel P.
Doctoral Committee Member(s):Abelson, John R.; Zuo, Jian-Min; Eckstein, James N.; Wagner, Lucas K.
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Rapid Materials Discovery
Transition metal chalcogenides
Antiferromagnetism
Incommensurate magnetic structure
Spin frustration
Co-existing magnetic phases
Abstract:Search for new functional inorganic materials has been a perennial focus of materials science and plays a crucial role in uncovering novel phenomena. One class of materials that has particularly drawn tremendous attention is that of transition metal chalcogenides exhibiting strong d-electron correlations. These materials result in a plethora of exotic physical phenomena such as superconductivity, metamagnetic metallic behavior, and quantum phase transitions via a complex interplay of spin, charge, lattice and orbitals degrees of freedom. Since the discovery of superconductivity in low-dimensional materials, there has been a growing thrust to understand the emergent phenomena that arise from strong electron correlations. This dissertation describes attempts to find new materials with low-dimensional magnets as one use case in the ternary chalcogenide phase space. This work utilizes two different approaches to look for new magnetic materials – discovery of new magnetic compounds and chemical substitution of existing compounds. Increased computing power and modern electronic structure calculations have tremendously aided the discovery of new materials. Core to this effort, however, is the validation of these predictions which demands versatile and efficient experimental methods. As a part of the first approach, novel transition metal chalcogenides will be explored using high-throughput experimental techniques, such as temperature and time-resolved in-situ x-ray diffraction, powered by computational predictions in the Ba–Ru–S and ternary chalcogenide phase diagrams of the form X–Y –Z (X = K, Na, Ba, Ca, Sr, La, K; Y is a 3d transition metal; and Z = S or Se) (by collaborating with computational scientists) In situ X-ray diffraction reveals the kinetic behavior of reagents, the course of their reaction, and the presence of any products regardless of their temperature existence window. The research presented here aims to bridge the gap between computational and experimental studies. New insights into prioritizing computationally predicted compounds will be suggested to guide experimental discoveries. The second approach to discovering new compounds involves perturbing the ground state of known magnetic materials by chemical substitution which will result in spin frustration thereby resulting in new magnetic ground states. Examples here will include the bond and geometric frustration in Mn1−xFexPSe3 and K2MnS2−xSex. The competing exchange interactions caused by bond frustration due to cation substitution and anisotropy will be studied in Mn1−xFexPSe3 to reveal co-existing nanoscale magnetic phases in this solid solution. Second, the interplay between various exchange interactions caused by geometry and anisotropy will be exploited to reveal an unexpected incommensurate magnetic ordering in K2MnS2−xSex previously identified as a simple antiferromagnetic structure.
Issue Date:2019-04-16
Type:Text
URI:http://hdl.handle.net/2142/105191
Rights Information:Copyright 2019 Ankita Bhutani
Date Available in IDEALS:2019-08-23
Date Deposited:2019-05


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