Browsing by Author "Mankey, Gary"
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Item Abstract: E5.00005 : Spin and Orbital Magnetic Moments of Fe and Co in Co/Fe and Fe/Co Multilayers on Si from L2,3 Edge X-ray Magnetic Circular Dichroism Spectroscopy*(2016) Mankey, Gary; University of Alabama TuscaloosaNanostructured FeCo thin films are interesting for magnetic recording applications due to their high saturation magnetization, high Curie temperature and low magnetocrystalline anisotropy. It is desirable to know how the magnetism is modified by the nanostructrure. We report Fe L₂,₃ edge and Co L₂,₃ edge x-ray magnetic circular dichroism (XMCD) investigations of element specific spin and orbital magnetism of Fe and Co in two multilayer samples: (S1) Si/SiO2/[Co 0.8 nm/Fe 1.6 nm]x32/W (2nm) and (S2) Si/SiO2/[Co 1.6 nm/Fe 0.8 nm]x32/W (2nm) thin films at room temperature. Sum rule analysis of XMCD at Fe L₂,₃ edge in sample S1 shows that the orbital moment of Fe is strongly enhanced and the spin moment is strongly reduced as compared to the values found in bulk Fe. Details of sum rule analysis will be presented to compare and contrast spin magnetic moments and orbital magnetic moments of Fe and Co in the two multilayer samples.Item Abstract: H29.00006 : The Quality Enhancement Plan Matrix (12 Years and Still Tweaking the Process!)(2009) Mankey, Gary; University of Alabama TuscaloosaAs an alumni of the 1997 New Faculty Workshop, I've had plenty of opportunities to experiment with the teaching methods introduced there. Most recently, faculty at UA have been asked to develop a Learner-Centered approach to teaching, where regular, timely and thorough assesments of student learning becomes a key component of the curriculum. This involves four phases: 1) Identifying and defining learning outcomes, 2) Matching assessments to outcomes, 3) Identifying baselines and progression toward benchmarks and 4) Documenting the process using a quality enhancement plan matrix. This has led to the development of learning tools designed to enhance critical thinking and problem solving skills. This will be discussed in the context of setting teaching goals for new faculty, including how to document the process for teaching portfolios.Item Anisotropy Graded Media: Extending the Superparamagnetic Limit (abstract)(2009-04-29) Mankey, Gary; University of Alabama TuscaloosaThe maximum storage density in magnetic media is limited by the superparamagnetic size of the grains that make up the bits. The superparamagnetic size can be reduced by increasing the anisotropy of the grains; however, in conventional media, in which the anisotropy of the grains is uniform, this leads to a proportionate increase in the switching field. The switching field, however, is limited by the maximum magnetization of the core material in the write head. Recent calculations have shown that the switching field can be significantly reduced relative to the thermal stability of the grains if the anisotropy is made to vary appropriately from the bottom to the top of the grain. In this project we propose to test this concept by fabricating and characterizing anisotropy graded films. We will use the hcp CoPtX system, with X = Cr or Ru, where the anisotropy gradient is obtained by grading the composition. Both sheet films and granular films will be fabricated. The anisotropy gradients will be determined by analyzing magnetization curves. Dynamic coercivity measurements will be used to determine the short-time coercivity and the zero-field energy barrier in the granular films. These results will be compared with similar measurements on films with uniform anisotropy films in order to test the predictions for graded media.Item Controlled Synthesis and Characterization of Magnetic Chalcospinels Nanocrystals(University of Alabama Libraries, 2020) Akbari Afkhami, Farhad; Gupta, Arunava; University of Alabama TuscaloosaBinary and ternary metal chalcogenides have become well-known materials among chemists, physicists, material scientists, and other researchers of the field, and they have attracted significant attention because of their novel chemical, magnetic, electronic, mechanical and optical properties. Among the metal chalcogenides, chromium-based chalcospinels ACr2X4 (A = Cu, Co, Fe, Cd, and Hg; X = S, Se, and Te) have gained significant attention because they are a notable class of magnetic materials such as semiconductors, magnetic metals, and insulators. In this work, a general overview of binary and ternary metal chalcogenides and their nanocrystals has been provided. We have also provided an overview of the wet-chemical colloidal methods as an important approach to size and shape-controlled synthesize of nanocrystals. We have also discussed the importance of metal doping reactions as a pathway to create previously unavailable multielemental materials for high-performance applications. In this set of studies, colloidal nanocrystals of chromium-based chalcospinels of CuCr2S4 and CuCr2Se4 have been synthesized via hot-injection and heat-up methods and were characterized using experimental methodology comprised of different microstructural and structural tests. The magnetic properties of these nanocrystals have also been studied. The next studied system was Cr-doped pyrite CuSe2 nanocrystals, eventually leading to the observation of significant enhancement of ferromagnetic moment by Cr-doping in octahedral sites of the pyrite structure. We performed a unique reaction in which nanocrystals of CrxCu1-xSe2 (x = 0.1-0.5) formed in the pyrite phase, which is not stable in bulk form. The host p-CuSe2 nanocubes did also undergo a degradation influenced by the reaction temperature and the doping of Cr3+ ions in the pyrite crystal structure. The Cr-doped nanocrystals of the pyrite phase were formed during the heat-up procedure and by increasing the reaction temperature transformed to CuCr2Se4 spinel nanocrystals. To the best of our knowledge, no cationic substitution of chromium for copper has been reported on pyrite CuSe2 systems so far, likely due to the significant size difference between chromium and copper. Therefore, the results of this work are a powerful approach for the design and fabrication of new multielemental materials that may not be stable in the bulk form.Item Deus ex machina: the God machine(University of Alabama Libraries, 2009) Pincumbe, Nicholas James; Martone, Michael; University of Alabama TuscaloosaGod is our salvation from eternal death. That's what Professor Nicholas Updown grew up believing. But what if there is no God? What then? These questions lead Nicholas down an unprecedented path of scientific exploration that unlocks the secrets to traveling through time. The wake of this discovery sweeps up a cast of odd and ambitious characters, including Updown's sultry wife, a no holds barred Presidential candidate, a mysterious hooded killer, a curious journalist, a crusading cop, the founder of Forever Life, and a whole slew of uniformed Time Travelers. Along the way, Nicholas Updown learns a thing or two about the secrets of the universe and those in his own life.Item Evaluation of Co80Pt20 Films for Power Inductor Applications(University of Alabama Libraries, 2021) Paul, Roni; Kotru, Sushma; University of Alabama TuscaloosaMagnetic components such as inductors and transformers are the largest components for power conversion circuits. There is a consistent effort to reduce the size of these components. Thin film technology is introduced to downsize these components, and ferrite films are used to build inductors. However, the core gets saturated at a very low current. Using a permanent magnet between the ferrite films can increase the saturation current by almost double. In this work, CoPt thin films were evaluated as a potential candidate material as a permanent magnet for such applications. CoPt films were deposited at room temperature using a magnetron sputtering system. CoPt films with four different thickness were deposited. The films were annealed in vacuum in the sputtering chamber at 700 ℃ for 30 minutes. XRD was done for phase identification. The thickness of these films was measured using a scanning electron microscope (SEM), and compositional analysis was done by Energy Dispersive Spectroscopy (EDS). The magnetitic studies on these films were performed using Alternating Gradient Magnetometer (AGM) and Vibrating Sample Magnetometer (VSM).Item The growth temperature and measurement temperature dependences of soft magnetic properties and effective damping parameter of (FeCo)-Al alloy thin films(American Institute of Physics, 2018-01-05) Ariake, Yusuke; Wu, Shuang; Kanada, Isao; Mewes, Tim; Tanaka, Yoshitomo; Mankey, Gary; Mewes, Claudia; Suzuki, Takao; University of Alabama Tuscaloosa; TDK CorporationThe soft magnetic properties and effective damping parameters of Fe73Co25Al2 alloy thin films are discussed. The effective damping parameter alpha(eff) measured by ferromagnetic resonance for the 10 nm-thick sample is nearly constant (approximate to 0.004 +/- 0.0008) for a growth temperature T-s from ambient to 200 degrees C, and then tends to decrease for higher temperatures and alpha(eff) is 0.002 +/- 0.0004 at T-s = 300 degrees C. For the 80 nm-thick sample, the alpha(eff) seems to increase with T-s from alpha(eff) = 0.001 +/- 0.0002 at T-s = ambient to alpha(eff) = 0.002 +/- 0.0004. The alpha(eff) is found nearly constant (alpha(eff) = 0.004 +/- 0.0008) over a temperature range from 10 to 300 K for the 10 nm films with the different T-s (ambient, 100 and 200 degrees C). Together with an increasing non-linearity of the frequency dependence of the linewidth at low Ts, extrinsic contributions such as two-magnon scattering dominate the observed temperature dependence of effective damping and linewidth. (C) 2018 Author(s).Item The Growth Temperature and Measurement Temperature Dependences of Soft Magnetic Properties and Effective Damping Parameter of (FeCo)-Al Alloy Thin Films(2018) Ariake, Yusuke; Wu, Shuang; Kanada, Isao; Mewes, Tim; Tanaka, Yoshitomo; Mankey, Gary; Mewes, Claudia; Suzuki, Takao; University of Alabama TuscaloosaItem Growth, Characterization, and Properties of Bismuth Ferrite-Based Multiferroic Complex Oxides(University of Alabama Libraries, 2022) Joshi, Chhatra Raj; Gupta, Arunava; Mankey, Gary; University of Alabama TuscaloosaMaterials that have at least two coupled electric, magnetic, and structural order parameters resulting in simultaneous ferroelectricity, ferromagnetism, and ferroelasticity are known as multiferroic materials. Bismuth ferrite (BiFeO3) is one of the most heavily studied room temperature single-phase multiferroic material. The simultaneous existence of ferroelectricity and antiferromagnetism with cross-coupling between these order parameters has driven intense research to accomplish electric field control of magnetism. To utilize these materials in electronic applications it is desirable to increase the magnetization and magnetoelectric coupling while reducing the switching voltage and leakage current. Tuning these responses can be achieved via strain and/or elemental engineering techniques. As the former is limited by the availability of suitable high-quality substrates for control of strain state, the latter is a more flexible technique. This thesis focuses on a systematic study of growth, structural, electrical, and magnetic characterizations of epitaxial thin films of multiferroic BiFeO3 (BFO) and Fe-site substituted BiFeO3. High-quality multiferroic epitaxial films of BiFeO3 on SrRuO3 buffered(001)-oriented SrTiO3 substrates fabricated using pulsed laser deposition are investigated. Switching dynamics of BiFeO3 have been explored using three fundamental scaling laws: Kittel's law, Kay-Dunn law, and the Ishibashi-Orihara model to acquire a complete description of the dynamical behavior and its relationship to the microstructure of the films. The primary goal of this work is to explore Fe-site substitution with magnetic elements Co and Mn, and non-magnetic element Al in BFO over a wide range of compositions. The enhancement of piezoelectric properties, electrical conductivity, and magnetic properties have been achieved through cobalt substitution. On the other hand, reduction in leakage current, and enhancement in magnetic and piezoelectric properties have been achieved through Al substitution. Moreover, we analyzed the switching dynamics in the time domain and corroborated the findings with the domain structure via a microscopy technique. It is demonstrated that Fe-site substitution of BFO is indeed a viable option to achieve improved characteristics required for device use. By identifying thebenefits of Fe-site substitution, this dissertation provides a pathway to explore BFO-based alternate magnetoelectric materials with desired properties for device applications.Item Investigation of Magnetic Anisotropies and Magnetization Dynamics in Soft Magnetic Materials(University of Alabama Libraries, 2020) Srivastava, Abhishek; Mewes, Tim; University of Alabama TuscaloosaMagnetic anisotropy and damping are two main properties that determine the characteristics of many magnetic devices such as inductors, transformers, hard drives, GMR sensors, MRAM etc. The magnetic materials used in these devices can be in different forms. For example spintronic devices are made of thin films (single crystalline or polycrystalline), and thus in these systems the effect of the substrate such as lattice mismatch, strain etc plays an important role in determining and manipulating magnetic properties. In case of transformers and inductors magnetic materials are made of bulk ferrite or as thin (~ 20 micrometer) ribbons of nanocomposite alloys. This dissertation gives a basic introduction of the magnetization dynamics and the physics and instrumentation of FMR. The induced anisotropy and magnetization dynamics of Co74.6Fe2.7Mn2.7Nb4Si2B14 (at %) melt-spun, soft magnetic alloy ribbons after various secondary processing treatments was studied by broadband ferromagnetic resonance (FMR) technique. A new method of determining the relative permeability of these ribbons is discussed and compared to the established vibrating sample magnetometry (VSM) and the toroid method. This new method of determining the permeability does not require information about the volume or mass of the sample nor does it require any special sample preparation procedure. Another study presented in this thesis investigates the temperature dependence of the magnetic anisotropy of a single crystal magnetite (Fe3O4) thin film on MgGa2O4 substrate. The aim of this study is to characterize the magnetization dynamics and magnetic anisotropy of this magnetite thin film through the Verwey transition. The FMR study of this film suggest a continuous structural transition from cubic to monoclinic phase as the temperature is decreased. Finally the magnetic properties of polycrystalline semiconducting spinel CdCr2S4 films grown by low-pressure metal organic chemical vapor deposition are studied. This includes the investigation of the paramagnetic to ferromagnetic phase transition using broadband FMR. The effective magnetization vs temperature data shows a relatively sharp transition compared to magnetization vs temperature data obtained from VSM. The study shows that these differences can be traced to the different roles the applied magnetic field has when analyzing the data from these two techniques.Item Investigation of Spinel Ferrite Thin Films for Spintronics Applications(University of Alabama Libraries, 2022) Regmi, Sudhir; Gupta, Arunava; LeClair, Patrick R.; University of Alabama TuscaloosaSpinel ferrite thin films have garnered special attention due to their usefulness in recent technological advances. They hold a significant promise for various device applications, including microwave devices, memory chips, transformer cores, antenna rods, and millimeter-wave integrated circuitry. These materials are attractive due to their extremely high specific resistance, high saturation magnetization, high Curie temperature, and exceptional flexibility in tailoring magnetic properties. In this dissertation, we attempt to address a most critical issue impeding the successful integration of spinel ferrites in ferrite-based microwave devices, spin-Seebeck effect (SSE)-based thermoelectric devices, and magnetostrictive device applications by presenting a successful fabrication and characterization of high-quality (Ni, Co, Fe)−Fe₂O₄ thin films with minimal defects, grown epitaxially on single crystalline lattice-matched substrates using the pulsed laser deposition method. Typically, spinel ferrite thin films such as NiFe₂O₄ (NFO), CoFe₂O₄ (CFO), and Fe₃O₄ (FFO), deposited by both physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques suffer from several structural defects resulting in degraded magnetic properties. These defects are primarily the formation of antiphase boundaries and misfit dislocations that result in low saturation magnetization and high magnetic saturation field. We show that by combining isostructural substrates with lower lattice-mismatch, as low as 0.06%, and optimum deposition parameters, one can successfully eliminate essentially all the film defects to obtain characteristics comparable to bulk single-crystal. We utilized spinel structured MgAl₂O₄, MgGa₂O₄, and ZnGa₂O₄ substrates for film growth with varying lattice mismatches with NFO, FFO, and CFO crystals. The deposited films are structurally mostly defect-free and have a smooth surface morphology with less than 200 pm root mean square (RMS) roughness. A 400 nm NFO film on ZnGa₂O₄ substrate shows uniaxial perpendicular anisotropy (Hu⊥ = 0.1 (±0.1) kOe), Gilbert damping parameter equal to αₑff = 9 × 10−⁴ (±7×10−⁵), and very low strain-induced anisotropy (Hσ = 0.4 (±0.1) kOe). It has also been demonstrated that similar improvements are attainable from other members of the spinel ferrite family with minimal substrate-induced film strain, such as a sharper Verwey transition in FFO films and a lower magnetoelastic uniaxial anisotropy in CFO films.Item Magnetic properties and structure of low temperature phase MnBi with island structure(American Institute of Physics, 2017-02-22) Ito, Masashi; Tanaka, Yoshitomo; Satoh, Takuya; Mankey, Gary; Schad, Rainer; Suzuki, Takao; University of Alabama Tuscaloosa; TDK CorporationThe magnetic properties of the lowtemperature phase (LTP) MnBi thin films of islands structure are discussed. The LTP MnBi islands are formed onto silica substrates after the multilayers {Bi(3.2nm)/Mn(2nm)}x N are deposited and then annealed at 450C for 0.5hr, where N is the number of the repetition of a pair of Mn and Bi layer. Those islands are found to be of the LTP MnBi, with the c-axis orientation along the normal to the sample plane for N= 10 similar to 40. Their size vary from place to place, but are averagely of about a few hundred nm in height and a few mu m in width for N from 10 to 40. For N= 200, the elongated islands are formed densely, with the length of about a few tens of mu m. The coverage of those islands increases with N. The temperature dependence of saturation magnetization Ms is qualitatively similar to that for bulk, though the absolute values for Ms are smaller by 20%. The magnetic anisotropy constants of K-u1 and K-u2 are evaluated for the samples with N= 10 similar to 40, where K-u1 and K-u2 are the magnetic anisotropy constants corresponding to the second and fourth power term in the uniaxial magnetic anisotropy energy expression. It is found that the K-u1 increases with T monotonously, reaching to about 1x10(7) erg/cc at 400K. On the other hand, the K-u2 remains nearly zero for temperatures below 300K, and then becomes negative, reaching to about 7 x 10(6) erg/cc at 400K. This is the first to report of the temperature dependence of K-u1 and K-u2 in the LTP MnBi of an island structure. It is also noted that the decrease of K-u for a temperature range beyond around 450 K is possibly due to the decrease of the K-u2 component, as demonstrated in the present study. (C) 2017 Author(s).Item Magnetic Properties of Coupled Gd/Pd/Ni Thin Films(2006) Mankey, Gary; University of Alabama TuscaloosaMagnetic properties of coupled Gd/Pd/Ni thin filmsILIR ZOTO,GARY MANKEY, MINT Center, Department of Physics, University of Alabama— Transition metal-rare earth bilayers might allow magnetizations higher than thatavailable from transition metal if the strong exchange interactions of the transitionmetal layer could be used to raise the Curie temperature of an adjacent, high momentrare earth layer. Literature suggested for a ferromagnetic interaction in the Ni-Gd bulk alloys and an increased moment at room temperature when Gd layer isdeposited onto thin Co and permalloy films. Recently, we found that Ni/Gd bilayerscouple antiferromagnetically at the interface. Adding a spacer layer could changethe coupling behaviour. Here, a study of a Gd(15nm)/Pd(tnm)/Ni(10nm) trilayeris presented with t varying from 0.5 to 2.5nm. The hysteresis loops were measuredwith VSM in the temperature range 5-250K. A Stoner-Wolfarth model simulates thehysteresis loops through the minimization of the energy of the following expression:E=−M₁Ht₁cos(θ₁)−M₂Ht₂cos(θ₂) +K₁t₁sin²(θ₁) +K₂t₂sin²(θ₂)+J₁cos(θ₁−θ₂) +J₂cos²(θ₁−θ₂)where J₁ and J₂ are the bilinear and biquadratic coupling constants. The simulatedloops are in good agreement with the experimental results and confirm the antifer-romagnetic coupling of Ni and Gd layers for t<2.5nm and the disappearance of thecoupling for t>2.5nm.Item Magnetic Properties of Low Temperature Phase MnBi of Island Structure(2016-02-29) Mankey, Gary; University of Alabama TuscaloosaThe magnetic and structural properties of island-structured LTP MnBi fabricated onto MgO single crystal substrates are discussed. The size and height of the “Volmer-Weber” type islands vary from place to place but are averagely a few microns and sub-microns, respectively. From the wetting angle (40 ∼ 60°) of those islands, the surface energy ΥMnBi of LTP MnBi is found to be 0.5∼0.8 J/m². Those MnBi islands possesses the magnetic anisotropy constant Kᵤ and saturation magnetization Mₛ close to those for bulk over a temperature range of 5 to 400 K. There seems to be a correlation between Ku and lattice constant c measured at 300K. The Kᵤ is found to be inversely proportional to Mₛ⁵ over the temperature range from 5 K to 400 K, as compared to the Mₛ⁸ dependence for those fabricated onto fused silica glass substrates.Item New soft magnetic materials for high frequency applications(University of Alabama Libraries, 2019) Wu, Shuang; Mewes, Tim; University of Alabama TuscaloosaSoft magnetic materials are widely used in devices such as inductors, transformers, antennas, magnetic hard drives, etc. Some of those devices will benefit greatly from operating at high frequencies. Thus fundamental study on finding the materials that have better soft magnetic properties is essential for improving the performance of those devices. Fe alloys have been proved to be promising candidates for high frequency applications. In this dissertation, an extensive study of magnetic properties of FeAl, (FeCo)-Al and (FeCo)-Si alloy thin films and their dependence on the film thickness and growth temperature has been presented. These films have body-centered cubic structure and columnar growth morphology. It is shown that the thickness of the film, which has an influence on the stress inside the film, may affect the coercivity through the magnetic-elastic coupling. The same mechanism is observed in the growth temperature dependence study, where reduced stress caused by increased growth temperature leads to a decrease in coercivity. The effective damping parameter shows a huge increase at small thickness due to the spin pumping effect. In-plane rotation ferromagnetic resonance measurements unveil the existence of four-fold anisotropy in (FeCo)-Si films. In addition, a four-fold symmetry is observed in the FMR linewidth vs. in-plane angle plot, which indicates anisotropic damping caused by the two-magnon scattering contribution. The film thickness dependence of FMR linewidth caused by the two-magnon scattering suggests that the origin of the two-magnon scattering is not pure interfacial.Item Radon Detection and 241Am-7Li Source Development for the Lux-Zeplin Dark Matter Experiment(University of Alabama Libraries, 2025) Sazzad, A. B. M. Rafi; Piepke, AndreasDark matter presents a conundrum at the intersection of particle physics and cosmology. Observational data from astronomy and precision cosmology have allowed scientists to calculate the relic abundance of dark matter with considerable accuracy. Yet, the exact nature of the dark matter particle remains a mystery. Theoretical models and hypotheses suggest that the mass of dark matter particle candidates ranges from as low as $10⁻²² eV/c² to as high as 10³ M_⊙(10⁷⁰ eV/c², spanning an astounding ~90 orders of magnitude! Of the numerous candidate particles, those that also resolve issues in the highly successful standard model of particle physics, are of particular interest to experimentalists. One such candidate is the Weakly Interacting Massive Particle (WIMP), which if it exists, could also resolve the gauge hierarchy problem in particle physics. WIMPs are theorized to interact with certain detector materials such as liquid xenon (LXe), via the weak force, active on all other known particles, and produce nuclear recoil (NR). However, this detection scheme meets several challenges. Firstly, the LXe must be sufficiently purified of radioactive impurities like ⁸⁵Kr and ²²²Rn to not overwhelm the rare NR signal events in terms of interaction rate. Secondly, the detector requires precise calibration of its response to NR-type interactions, specifically in the energy region where WIMP interactions are expected. In this thesis, I describe my contributions to the ongoing direct dark matter search experiment called LUX-ZEPLIN (LZ). Most of my work relates to the preparation of the experiment, namely the measurement of the release of trace amounts of radon gas from detector materials, forming the dominant background component. This work was important to ensure a low detector background and, with it, high sensitivity to dark matter. As a second contribution, I participated in all phases of the development, manufacture, testing and calibration of AmLi neutron sources important for mapping out the NR band for WIMP detection. Both subjects have been documented in publications with me as the first author; the work was performed at UA. The thesis, furthermore, describes my data analysis effort, utilizing AmLi source calibration data to help establish the WIMP event parameter range in LZ.Item Silver-Based Metal-Organic Frameworks for Microbial Mitigation(University of Alabama Libraries, 2022) Zolghadr, Ehsan; Leclair, Patrick Pl; Elliott, Mark; University of Alabama TuscaloosaMetal-organic frameworks (MOFs) have recently emerged as promising materials for numerous antimicrobial applications due to their unique properties such as porosity, tunability, and high ion release rate. One of the applications is utilizing them as antimicrobial agents to tackle biofouling phenomena in membrane-based water purification through surface functionalization which is a promising approach to improve the biofouling resistance of polymeric membranes. The main body of this dissertation covers a novel ultrasonic-assisted technique to modify polyvinylidene fluoride (PVDF) microfiltration membranes by silver-based metal-organic frameworks (AgMOFs). Different morphological and characterization techniques were employed to indicate that the in-situ growth of AgMOFs was successful by this facile method. The AgMOFfunctionalized membrane also showed enhanced static antibacterial activities and dynamic biofouling resistance compared to those of the pristine membrane while in contact with the model bacteria, Escherichia coli and Staphylococcus aureus. Moreover, as a side study, AgMOF and its graphene oxide (GO)-decorated nanocomposite (GO AgMOF) are proposed as potential antimicrobial candidates for cancer treatment.Item Soft magnetic properties and damping parameter of (FeCo)-Al alloy thin films(American Institute of Physics, 2017-02-06) Kanada, Isao; Cruce, Alex; Mewes, Tim; Wu, Shuang; Mewes, Claudia; Mankey, Gary; Suzuki, Takao; University of Alabama Tuscaloosa; TDK CorporationFor high frequency device applications, a systematic study of the soft magnetic properties and magnetization dynamics of (FeCo)-Al alloy thin films has been carried out. A low effective damping parameter alpha(eff) of 0.002 and a high saturation magnetization of about 1,800 emu/cc are obtained at y=0.2 similar to 0.3 for (Fe1-yCoy)(98)Al-2 alloy thin films deposited onto fused silica and MgO(100) at an ambient temperature during deposition. Those films are of the bcc structure with the <110> orientation normal to the film plane. They possess a columnar structure, grown along the film normal. The column width is found to be about 20 nm for y=0.25. It is concluded that the (FeCo)-Al thin films with a damping parameter as low as 0.002 and high saturation magnetization of about 1,800 emu/cc have been successfully fabricated, and that they are potential for future high frequency device applications. (C) 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Item Soft Magnetic Properties and Damping Parameter of (FeCo)-Al Alloy Thin Films(2017) Kanada, Isao; Cruce, Alex; Mewes, Tim; Wu, Shuang; Mewes, Claudia; Mankey, Gary; Suzuki, Takao; University of Alabama TuscaloosaFor high frequency device applications, a systematic study of the soft magnetic properties and magnetization dynamics of (FeCo)-Al alloy thin films has been carried out. A low effective damping parameter αeff of 0.002 and a high saturation magnetization of about 1,800 emu/cc are obtained at y=0.2∼0.3 for (Fe1-yCoy)98Al2 alloy thin films deposited onto fused silica and MgO(100) at an ambient temperature during deposition. Those films are of the bcc structure with the <110> orientation normal to the film plane. They possess a columnar structure, grown along the film normal. The column width is found to be about 20 nm for y=0.25. It is concluded that the (FeCo)-Al thin films with a damping parameter as low as 0.002 and high saturation magnetization of about 1,800 emu/cc have been successfully fabricated, and that they are potential for future high frequency device applications.Item Study of thermoelectric generators and perovskite solar cells for renewable energy applications(University of Alabama Libraries, 2020) Ouyang, Zhongliang; Li, Dawen; University of Alabama TuscaloosaThis dissertation aims at explorations of two promising renewable energy devices: one is thermoelectric generators (TEGs) and the other is perovskite solar cells (PVSCs). The first half of this dissertation (Chapter 2 & 3) focuses on the simulation study of TEGs while the second half (Chapter 4 & 5) concentrates on the experimental study of PVSCs. Chapter 1 serves as an overall introduction of TEGs and PVSCs. Chapter 2 investigates simulation of segmented TEGs with various state-of-the-art thermoelectric (TE) materials between 300 K and 1000 K. The influence of thermal radiation, electrical and thermal contact effects have been studied. The results show that these effects, if well-regulated, do not prevent segmented TEGs from achieving high efficiency and output power density. In Chapter 3, segmented TEGs have been further modelled to find out the best cost-performance ratios. The results reveal that successful segmentation of TE materials can offer a cost-performance ratio of ~0.86 $ W-1, less than commercially desired cost-effectiveness of 1 $ W-1, while maintaining an efficiency of 17.8% and delivering a power density over 3 Watt cm-2. These results predict the commercial feasibility and competitiveness of segmented TEGs in the same dollar per watt metrics as other renewable energy devices. Chapter 4 presents a rapid layer-specific annealing on perovskite active layer enabled by ultraviolet (UV) light-emitting diode (LED) and efficiency close to 19% is achieved in a simple planar inverted structure. These results justify that if the UV dosage is well-managed, UV light is capable of annealing perovskite into high-quality film rather than simply damaging it. Moreover, the layer-specific photonic treatment allows accurately estimating the deposition energy required to form perovskite film at device quality level. Chapter 5 exhibits an effort towards scalable manufacturing of perovskite solar panels. Perovskite mini-modules have been demonstrated with blade-coating and rapid thermal processing (RTP) in ambient environment. Mini-modules with an active area over 2.7 cm2 exhibit a champion efficiency of 17.73%. These results pave the way for large-scale production of PVSCs through high-speed roll-to-roll printing. Chapter 6 summarizes the conclusions and proposes a possible future work.