Condensed Matter Physics Commons^™

Synthesis And Characterization Of Doped Rare-Earth Zinc Alloys, Partha Das

Graduate Theses/Dissertations

Rare-Earth-Zinc (RE-Zn) alloys doped with manganese represent a promising class of materials with diverse applications in magnetic, electronic, and thermoelectric devices. These alloys hold significant potential owing to the unique combination of rare-earth elements' properties with the versatility of zinc, augmented by manganese doping. In this study, I present the successful synthesis of ErMn_0.2Zn_11.8 alloys, achieved through self-flux method. The synthesized crystals were characterized using electron dispersive spectroscopy (EDS) and single crystal X-ray diffraction (XRD). Additionally, magnetic measurements were performed to investigate the magnetic properties. Future plans include DFT calculations and comparison study between Rare-Earth-Zinc alloys with …

Spin And Charge Transport In Metallic Ferrimagnets And Disordered Magnetic Oxides, Leopoldo A. Hernandez

Electronic Theses and Dissertations

Recent efforts have been exploring the use of thin film synthetic ferrimagnets and disordered magnetic oxides for applications in spintronic devices. Due to the antiferromagnetic exchange interaction, ferrimagnetic materials offer the ultrafast dynamics of the antiferromagnetic exchange, with a net magnetization that can be influenced externally. With two, or more, competing ferromagnet sublattices, interesting properties arise that depend on the final magnetic landscape after growth of the material and it’s inherent magnetic anisotropy energies. Properties such as magnetic compensation temperatures, and perpendicular magnetic anisotropy are attractive for applications in spintronic memory and logic devices, some already being implemented in MRAM …

Magnetic Properties Of Zgnrs With Nitrogen And Fluorine Adsorbates, A Computational Study, Justin Petit

Electronic Theses and Dissertations

Imposing dimensional restrictions on graphene sheets and adding impurities can give rise to carbon nanostructures with magnetic properties. In this work, zigzag graphene nanoribbons, zGNRs, with nitrogen and fluorine adatoms are investigated for magnetic properties of interest for spin devices. Geometry optimizations were done determining which position along a zGNR electrode that N and F would favorably attach to. Edge positions were determined as the most stable attachment site. M-cell zGNR electrodes (M = 1-3) edge-functionalized by N and F adatoms were investigated with respect to their band structures and spin densities in antiferromagnetic and ferromagnetic, AFM and FM, configurations. …

Interfacial Magnetism And Anisotropy In Dirac And Weyl Semimetals, Noah Schulz

USF Tampa Graduate Theses and Dissertations

Semimetals have gained intense interest recently due to their exotic magnetic and electronic properties. One of the most widely studied semimetals is graphene, a Dirac semimetal. The utilization of graphene in devices and sensors requires interfacing it with other materials, which may induce potentially strong interfacial effects. Furthermore, graphene alone does not possess magnetic order. Studying the interfacial effects between graphene and magnetic materials is therefore of great importance in the application of graphene to meet modern technological needs. Furthermore, by understanding the fundamental interfacial physics between graphene and magnetic materials, new properties can be unlocked, broadening the possible applications …

Driven Magnetic Vortex Dynamics, Chase Hickman

Honors College Theses

Magnetic materials possess properties that allow for efficient data storage and transmission. Two important magnetic phenomena are domains and spin waves, both of which are active areas of research. Domains are regions of locally aligned magnetic moments within a material and spin waves are propagating disturbances in the alignment of those moments. A specific type of domain occurs when moments align to form a topological structure known as a magnetic vortex. Vortices are composed of a swirling in-plane magnetization centered around a localized region of out-of-plane magnetization known as a vortex core. A vortex has an in-plane chirality and out-of-plane …

X-Ray Absorption And Related Studies In Superconducting Devices And Magnetic Thin Films, Ghadendra Bahadur Bhandari

Graduate Theses, Dissertations, and Problem Reports (ETD)

Superconducting and magnetic thin films are commonly used in sensors for analytical detectors, especially those that operate at very low temperatures, often below 1 Kelvin. These highly sensitive detectors, capable of functioning across a broad range of wavelengths, have garnered significant interest in scientific research. The focus of this thesis is to address a material challenge associated with an emerging technology known as microwave kinetic inductance detectors (MKIDs). The research involves the study of Al/Si and Al-Mn/Si-based thin films, as well as an investigation into the magnetic properties of LaMnO₃ thin films. LaMnO₃, a perovskite thin film that plays a …

Thermal, Magnetic, And Electrical Properties Of Thin Films And Nanostructures: From Magnetic Insulators To Organic Thermoelectrics, Michael J. M. Roos

Electronic Theses and Dissertations

Modern fabrication and growth techniques allow for the development of increasingly smaller and more complex solid state structures, the characterization of which require highly specialized measurement platforms. In this dissertation I present the development of techniques and instrumentation used in magnetic, thermal, and electrical property measurements of thin films and nanostructures. The understanding of trapped-flux induced artifacts in SQUID magnetometry of large paramagnetic substrates allows for the resolution of increasingly small moments. Using these methods, the antiferromagnetic coupling of the interface between a Y₃Fe₅O₁₂ film and Gd₃Ga₅O₁₂substrate is quantitatively …

Synthesis And Characterization Of Cage-Structured Compounds As Promising Thermoelectric Materials, Nusrat Yasmin

Graduate Theses/Dissertations

The development of new thermoelectric materials is of great interest due to their potential to convert waste heat into useful electricity. The primary problem is that the physical factors that are utilized to assess thermoelectric performance conflict with one another. One way to improve their performance is to hinder the lattice from conducting heat through its vibrations while maintaining the heat conduction via the electrons. This can be done by creating cage structures that allow heavy atoms to jiggle. In this study, we report the synthesis of a group of such compounds, using the self-flux method. They all belong to …

Study Of Electronic And Magnetic Properties Of Bilayer Graphene Nanoflakes And Bimetallic Chalcogenides Using First-Principles Density Functional Theory And Machine Learning, Dharmendra Pant

Dissertations, Master's Theses and Master's Reports

Graphene, a one-atom-thick material, has been a wonder material since its discovery because of its superlative electronic, mechanical, and optical properties. When a layer of graphene is rotated over another layer, it exhibits many intriguing behaviors, ranging from superconductivity to the anomalous Hall effect to ferromagnetism at a magic angle of 1°, and hence the twisted bilayer graphene has been the subject of intense research in recent years. The surge in interest in this moiré structure can be attributed to the emergence of electronic flat minibands near the magic angle. Here, we studied the electronic and magnetic properties of twisted …

Controlling Electro-Magnetic Functionality Of Ruthenates By Heterostructure Design, Zeeshan Ali

LSU Doctoral Dissertations

Perovskite oxides (ABO₃) show wide range of functionalities originating from interplay of structural, spin, charge, and orbital degrees of freedoms. The bulk perovskite structure could be controlled via conventional chemical substitution, though exploiting heterostructure engineering novel ground states could be observed which otherwise are absent in bulk. In this thesis, the interest is to explore the electro-magnetic phenomena as complex oxides are confined in heterostructures.

I first investigate electromagnetic properties of ultrathin epitaxial ruthenate: SrRuO₃ (SRO); spatially confined between SrTiO₃ (STO) i.e., STO⁵-SROⁿ-STO⁵ with n = 1- and 2-unit cells. It …

Stability Of Two-Dimensional Magnetic Skyrmions, Amel Derras-Chouk

Dissertations, Theses, and Capstone Projects

Magnetic skyrmions are whirls formed by magnetic moments in a crystal. They have attracted attention largely due to their topological protection, which provides an avenue for technology like next-generation memory storage. The idea of topologically protected solutions of a quantum field theory was originally proposed by Tony Skyrme when he developed a model to explain the stability of hadrons in particle physics. His work has extended far beyond his original intent to several areas of condensed matter physics. Here we focus on skyrmions in magnetic materials.

Skyrme's original theory modeled excitations which exist in three spatial dimensions, a requirement for …

Magnetism Of Novel Rare-Earth-Free Intermetallic Compounds, Haohan Wang

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

Rare-earth-free magnets have drawn lots of interest because of their low cost, and the production is not limited by the shortage of rare-earth elements. This dissertation focuses on three rare-earth-free materials, Fe-Co-Ti alloys, Fe-Ni-B alloys, and Co-Si. All of them are synthesized by arc melting followed by melt-spinning. Fe_3+xCo_3−xTi₂ (x = 0, 2, 3) alloys exhibit hexagonal crystal structures and show non-collinear spin structures according to neutron diffraction. The magnetic moments have projections on both the c-axis and basal plane, and the corresponding misalignment angle exhibits a nonlinear decrease with …

Controlling Magnetic Exchange And Anisotropy By Nonmagnetic Ligand Substitution In Layered M P X 3 ( M = Ni , Mn; X = S , Se), Rabindra Basnet, Kamila M. Kotur, Milosz Rybak, Cory Stephenson, Samuel Bishop, Carmine Autieri, Magdalena Birowska, Jin Hu

Physics Faculty Publications and Presentations

Recent discoveries in two-dimensional magnetism have intensified the investigation of van der Waals magnetic materials and further improved our ability to tune their magnetic properties. Tunable magnetism has been widely studied in antiferromagnetic metal thiophosphates MPX3. Substitution of metal ions M has been adopted as an important technique to engineer the magnetism in MPX3. In this work, we have studied the previously unexplored chalcogen X substitutions in MPX3 (M=Mn/Ni; X=S/Se). We synthesized the single crystals of MnPS3−xSex (0≤x≤3) and NiPS3−xSex (0≤x≤1.3) and investigated the systematic evolution of the magnetism with varying x. Our study reveals the effective tuning of magnetic …

Exploring Tunable Magnetization And High-Temperature Ferromagnetism In Ternary Transition Metal-Based Chalcogenides, Hector Iturriaga

Open Access Theses & Dissertations

The discovery of long-range magnetic ordering in ultrathin transition metal-based compounds shows great promise for the development of nanoscale memory and spintronic devices. Composed of cost-effective materials and boasting from strong chemical and thermal stability at low dimensions, van der Waals (vdW) ternary transition metal chalcogenide magnets like CrSiTe3 (CST), Fe2.7GeTe2 (FGT), and Mn3Si2Te6 (MST), provide not only possible energy solutions, but also a broad platform to explore the versatile magnetic character of this family of compounds. Although they have great potential, it has been found that their long-range magnetic ordering exists at temperatures far too low (the highest of …

Evolution Of The Magnetic Properties On Van Der Waals Layered Magnets Via Pressure And Proton Irradiation, Rubyann Olmos

Open Access Theses & Dissertations

Probing the magnetism in quasi two-dimensional materials has the potential in driving their properties towards future use in spin electronic based devices. Studying such layered magnets will enable the scientific community to uncover tunable exotic phases such as superconductivity, quantum paramagnetism, etc. This work examines the influence of two types of external perturbations, namely, the pressure and proton irradiation, on the magnetic properties of several compounds in the van der Waals crystal family.

Pressure has been found to induce structural and magnetic phase transitions in many of these materials. Using hydrostatic pressure as a disorderless approach to manipulate the interlayer …

Magnetism In Curved Geometries, R. Streubel, Evgeny Y. Tsymbal, P. Fischer

Evgeny Tsymbal Publications

No abstract provided.

Experimental Exploration Of Shared Magnetic Phases Between Diverse Systems Of Iron-Pnictide Superconductors, Ryan Scott Stadel

Graduate Research Theses & Dissertations

The exciting field of iron-pnictide superconductors offers unique opportunities for studying the relationship between magnetism and unconventional superconductivity. This is vital to developing an understanding of the microscopic origin of high-temperature superconductivity, which is itself an important step in harnessing such a potentially revolutionary technology.

Polycrystalline and crystalline samples are synthesized over a diverse collection of related iron-pnictide systems including (Ca,Sr,Ba)1-xNaxFe2As2, Ba(Fe1-xCox)2As2 (122s), and LaFeAs1-xPxO, and TbFeAs1-xPxO (1111s). These compounds are characterized through various types of neutron and x-ray diffraction on multiple instruments, as well as muon spin resonance, and magnetic susceptibility measurements.

A thorough investigation into the conditions under …

Experimental And Computational Exploration Of The Dilute Magnetic Delafossite Cual1-Xfexo2 Alloys, Mina Aziziha

Graduate Theses, Dissertations, and Problem Reports (ETD)

CuAlO₂ is among several ternary delafossites, which is a rare p-type semiconductor with potential applications as a transparent conductive oxide, photocatalyst, and spintronics when doped with transition metal ions. Reported in this thesis are results from our investigations of CuAl_1-xFe_xO₂ (x = 0 to1) with a focus on the x-dependence of structural, magnetic, vibrational, optical properties, and the role of defects and impurities. Samples are prepared by solid-state reactions.

We performed a complete study of magnetic properties to investigate the possibility of room temperature ferromagnetic alloys, which are used in …

Development Of Software Tools And Experimental In Situ Electron Spin Resonance For Characterizing The Magnetic And Electrocatalytic Properties Of Transition Metal Chalcogenide Crystals, Jose Armando Delgado

Open Access Theses & Dissertations

Studying the magnetic properties and crystal defects of transition metal chalcogenide crystals is of paramount importance for utilizing them for next generation spintronics devices and hydrogen evolution reaction catalysts. Hydrothermally grown transition metal chalcogenide nanocrystals (MoS2, Ru2S3, Rh2S3, Co2S8) were chosen as catalysts for the hydrogen evolution reaction due to their low dimensionality and previous utilization as catalysts for hydrodesulfurization. The relationship between crystal defect sites and catalytic activity must be discerned to maximize the efficiency of hydrogen production during the hydrogen evolution reaction. ESR spectroscopy was utilized as a spin sensitive technique to study the defects and local changes …

Depth Dependent Atomic Valence Determination In La0.7sr0.3mno3 Thin Films Using Synchrotron Techniques, Robbyn B. Trappen

Graduate Theses, Dissertations, and Problem Reports (ETD)

The valence of atoms often has a strong effect on the properties of materials, such as magnetism, conductivity, and superconductivity. The atomic valence is often perturbed at the surface and/or interface and this deviation may play a strong role in many physical phenomena such as interfacial coupling and dead layers, both magnetic and electric. In this dissertation, I present a non-destructive approach of combining two X-ray absorption detection modes, electron yield and fluorescence, with very different probing depths in conjunction with theory to map out the layer-by-layer valence of a thin film.

The weighted average Mn atomic valence as measured …

Observation Of A Pressure-Induced Transition From Interlayer Ferromagnetism To Intralayer Antiferromagnetism In Sr4Ru3O10, H. Zheng, W. H. Song, J. Terzic, H. D. Zhao, Y. F. Ni, Lance E. Delong, P. Schlottmann, G. Cao

Physics and Astronomy Faculty Publications

Sr₄Ru₃O₁₀ is a Ruddlesden-Popper compound with triple Ru-O perovskite layers separated by Sr-O rock-salt layers. This compound presents a rare coexistence of interlayer (c-axis) ferromagnetism and intralayer (basal-plane) metamagnetism at ambient pressure. Here we report the observation of pressure-induced, intralayer itinerant antiferromagnetism arising from the interlayer ferromagnetism. The application of modest hydrostatic pressure generates an anisotropy that may cause a flattening and a tilting of RuO₆ octahedra. All magnetic and transport results from this study indicate these lattice distortions diminish the c-axis ferromagnetism and basal-plane metamagnetism, and induce a basal-plane antiferromagnetic state. …

Ambipolar Ferromagnetism By Electrostatic Doping Of A Manganite, L. M. Zheng, X. Renshaw Wang, W. M. Lü, C. J. Li, Tula R. Paudel, Z. Q. Liu, Z. Huang, S. W. Zeng, Kun Han, Z. H. Chen, X. P. Qiu, M. S. Li, Shize Yang, B. Yang, Matthew F. Chisholm, L. W. Martin, S. J. Pennycook, Evgeny Y. Tsymbal, J. M. D. Coey, W. W. Cao

Evgeny Tsymbal Publications

Complex-oxide materials exhibit physical properties that involve the interplay of charge and spin degrees of freedom. However, an ambipolar oxide that is able to exhibit both electron-doped and hole-doped ferromagnetism in the same material has proved elusive. Here we report ambipolar ferromagnetism in LaMnO₃, with electron–hole asymmetry of the ferromagnetic order. Starting from an undoped atomically thin LaMnO₃ film, we electrostatically dope the material with electrons or holes according to the polarity of a voltage applied across an ionic liquid gate. Magnetotransport characterization reveals that an increase of either electron-doping or hole-doping induced ferromagnetic order in this …

Magnetic Phases Of Large-Spin Ultracold Bosons: Quantum Dimer Models And Spin Liquid Phases, Todd C. Rutkowski

Graduate Dissertations and Theses

This thesis investigates the plausibility of producing a quantum spin liquid (QSL) with ultracold bosonic atoms optically confined to the Mott insulating state. QSLs have received a great deal of attention for being an antiferromagnetic groundstate with many exotic properties, including the absence of local order, long-range entanglement, and fractionalized excitations. However, the identification and characterization of these phases in solid state systems remains a great challenge. Here we outline an alternate route to uncovering the QSL phase, which from the nature of spin angular momentum for ultracold atoms encounters many properties unique to these systems along the way. This …

Non-Centrosymmetric Superconductivity And Magnetism In The Presence Of Broken Symmetries, Mojammel Alam Khan

LSU Doctoral Dissertations

Non-centrosymmetric (NC) superconducting and magnetic compounds have been synthesized and investigated using magnetic, specific heat, and transport measurements, as well as by neutron scattering and quantum oscillations. The crystal structures of NC compounds are defined by the lack of an inversion center. In NC superconductors, a finite antisymmetric spin orbit coupling originating from broken inversion symmetry results in unconventional Cooper pairing. Instead of a single spin channel, the order parameter is a mixture of spin-singlet and spin-triplet states. For NC magnetic compounds, the antisymmetric and isotropic spin interactions compete, leading to a helical ground state.

We have studied the NC …

Suppression Of Magnetism In Ba5Alir2O11: Interplay Of Hund's Coupling, Molecular Orbitals, And Spin-Orbit Interaction, Sergey V. Streltsov, Gang Cao, Daniel I. Khomskii

Center for Advanced Materials Faculty Publications

The electronic and magnetic properties of Ba₅AlIr₂O₁₁ containing Ir-Ir dimers are investigated using the generalized gradient approximation (GGA) and GGA + spin-orbit coupling (SOC) calculations. We found that the strong suppression of the magnetic moment in this compound recently found by Terzic et al. [Phys. Rev. B 91, 235147 (2015)] is not due to charge ordering but is related to the joint effect of the spin-orbit interaction and strong covalency, resulting in the formation of metal-metal bonds. They conspire and act against the intraatomic Hund's rule exchange interaction to reduce total magnetic moment of the …

Fabrication And Study Of The Structure And Magnetism Of Rare-Earth Free Nanoclusters, Bhaskar Das

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

No abstract provided.

Ground-State Tuning Of Metal-Insulator Transition By Compositional Variations In Bair1−XRuXO3 (0 ≤ X ≤ 1), Shujuan Yuan, Kamal H. Butrouna, Jsaminka Terzic, Hao Zheng, Saicharan Aswartham, Lance E. Delong, Feng Ye, P. Schlottmann, Gang Cao

Physics and Astronomy Faculty Publications

Hexagonal BaIrO3 is a magnetic insulator driven by the spin-orbit interaction (SOI), whereas BaRuO₃ is an enhanced paramagnetic metal. Our investigation of structural, magnetic, transport, and thermal properties reveals that substitution of Ru⁴⁺ (4d⁴) ions for Ir⁴⁺ (5d⁵) ions in BaIrO₃ reduces the magnitudes of the SOI and a monoclinic structural distortion and rebalances the competition between the SOI and the lattice degrees of freedom to render an evolution from a magnetic insulting state to a robust metallic state. The central findings of this paper are as follows: (1) light …

Electronic Structure And Stability Of Ligated Superatoms And Bimetallic Clusters, William H. Blades

Theses and Dissertations

Quantum confinement in small metal clusters leads to a bunching of states into electronic shells reminiscent of shells in atoms. The addition of ligands can tune the valence electron count and electron distribution in metal clusters. A combined experimental and theoretical study of the reactivity of methanol with Al_nI_m⁻ clusters reveals that ligands can enhance the stability of clusters. In some cases the electronegative ligand may perturb the charge density of the metallic core generating active sites that can lead to the etching of the cluster. Also, an investigation is conducted to understand how the bonding …

Effects Of Disorder And Low Dimensionality On Frozen Dynamics In Ca3co2-Xmnxo6, Brian Wesley Casas

USF Tampa Graduate Theses and Dissertations

Complex oxides represent an intersection of play grounds for the existence of exciting new fundamental physics and materials with potential technological implications. The realization of many exciting properties of these systems rely on the coupling of electronic, structural and magnetic degrees of freedom. Additionally, competing interactions within each type of coupling discussed previously lead to theoretically diverse ground states, which under the application of an external perturbation, can be tuned and probed.

Ca3Co¬2-xMnxO6 represent a quasi-one dimensional Ising spin chain system oriented in an antiferromagnetic triangular lattice. The exotic behavior of the undoped compound Ca3Co2O6 has inspired work on continuing …

Evolution Of Magnetism In The Single-Crystal Honeycomb Iridates (Na1−XLiX)2Iro3, Gang Cao, Tongfei Qi, L. Li, Jsaminka Terzic, Vincent Shian Cao, Shujuan Yuan, M. Tovar, Ganpathy Murthy, Ribhu K. Kaul

Physics and Astronomy Faculty Publications

We report the successful synthesis of single crystals of the layered iridate (Na_1−xLi_x)₂IrO₃, 0 ≤ x ≤ 0.9, and a thorough study of its structural, magnetic, thermal, and transport properties. This compound allows a controlled interpolation between Na₂IrO₃ and Li₂IrO₃, while maintaining the quantum magnetism of the honeycomb Ir⁴⁺ planes. The measured phase diagram demonstrates a suppression of the Néel temperature T_N at an intermediate x, indicating that the magnetic orders in Na₂IrO₃ and Li₂IrO_{3 …}