Effect of microstructure on the magnetic properties of transition metal implanted TiO2 films

The combined electronic, optic and magnetic properties of transition metal (TM) implanted ferromagnetic TiO2 is of interest for spintronic applications. The nature of the observed abundant ferromagnetism in such materials has been investigated for more than one and a half decades, yet still no clear explanation for its appearance can be given. In this thesis, the origin of the ferromagnetic order in TM:TiO2 systems is studied by investigating the interplay between structural order, defects and incorporation of implanted ions within the host lattice. The defect properties of the host TiO2 are altered by preparing different microstructures of TiO2 (e.g. amorphous, polycrystalline anatase and epitaxial anatase). The difference in microstructure is also found to influence the incorporation of the implanted ions with the host lattice. The crystallographic incorporation of the implanted TM atoms is found only in crystalline films. Moreover, it is observed that the suppression of the dopant related secondary phases can also be achieved by changing the microstructure. The obtained experimental results are compared with the existing theoretical frameworks, while the most relevant one describing our findings is elucidated. Based on this discussion, we propose an ideal microstructural candidate for a dilute magnetic oxide material based on our results.:1 Introduction 2 1.1 Spintronics 2 1.2 Dilute magnetic oxides 5 2 Fundamentals 13 2.1 Introduction 13 2.2 Magnetism in diluted magnetic oxides 13 2.2.1 Possible locations of dopant 3d ions in an oxide matrix 14 2.2.2 Mean field model 15 2.2.3 Bound magnetic polaron model 16 2.2.4 Charge transfer model 17 2.2.5 Ferromagnetism in undoped oxides 19 2.2.6 Extrinsic sources of ferromagnetism 20 2.3 Motivation 21 3 Experimental 24 3.1 Sample preparation 24 3.1.1 DC magnetron sputtering 24 3.1.2 Ion implantation 27 3.2 X-ray methods 29 3.2.1 X-ray diffraction 29 3.2.2 X-ray absorption 31 3.2.2.1 Synchrotron radiation 31 3.2.2.2 Physics of X-ray absorption 31 3.3 SQUID magnetometry 35 3.3.1 Avoiding magnetic contamination 37 3.4 Positron annihilation spectroscopy 38 4 TM Implantation into Different TiO2 Structures (TM = Co, Mn, V) 43 4.1 Experiments 43 4.2 Co+ implantation: from diluted paramagnetism to superparamagnetic clusters 45 4.2.1 Cluster-free Co+-implanted TiO2 thin films 45 4.2.1.1 Experiments 45 4.2.1.2 Structural properties 46 4.2.1.3 Implantation-induced structural defects 47 4.2.1.4 Magnetic properties 50 4.2.1.5 Local environment of implanted Co atoms 51 4.2.1.6 Summary 52 4.2.2 Revealing nano-clusters within Co+-implanted TiO2 thin films 54 4.2.2.1 Experiments 54 4.2.2.2 Structural properties 54 4.2.2.3 Magnetic properties 57 4.2.2.4 Local environment of implanted Co atoms 59 4.2.2.5 Summary 61 4.3 Mn+ implantation: from a non-magnet to a ferromagnet 63 4.3.1 Experiments 63 4.3.2 Relation between lattice damage and defects 64 4.3.3 Electrical transport properties 65 4.3.4 Local environment of implanted Mn atoms 66 4.3.5 Magnetic properties 67 4.3.6 Summary 69 4.4 V+-implanted TiO2 thin films 71 4.4.1 Experiments 71 4.4.2 Magnetic properties 71 4.4.3 Summary 74 5 The effect of the open volume defects on the magnetic properties of V:TiO2 films prepared by doping during deposition 76 5.1 Experiments 76 5.2 Structural Properties 77 5.3 Investigation of the open volume defects 78 5.4 Magnetic, optical and electrical properties 79 5.5 Summary 81 6 Conclusions 84 6.1 Defects in TiO2 84 6.2 Formation of secondary phases 85 6.3 Evolution of the ferromagnetism in different microstructures of TiO2 87 7 Acknowledgments 91Die kombinierten elektrischen, optischen und ferromagnetischen Eigenschaften von TiO2, welches mit einem Übergangsmetall (TM) dotiert wurde, sind für Anwendungen in der Spintronik von hoher Bedeutung. Obwohl dieses Material seit mehr als anderthalb Jahrzehnten untersucht wird, kann derzeit noch keine eindeutige Erklärung für den beobachteten Ferromagnetismus gegeben werden. In dieser Arbeit wird die Ursache für die ferromagnetische Ordnung in TM:TiO2-Systemen untersucht, indem der Zusammenhang von struktureller Ordnung, Defekten und der Einlagerung der implantierten Ionen im Wirtsgitter analysiert wird. Durch die Verwendung unterschiedlicher Mikrostrukturen (z.B. amorphes, polykristalliner Anatas und epitaktischer Anatas) wurden auch die Defekteigenschaften des Wirts-Titanoxid variiert. Dabei zeigte sich ein Einfluss der unterschiedlichen Mikrostrukturen auf die Einlagerung der implantierten Atome in das Wirtsgitter. So konnte die Substitution von Ti-Atomen durch Atome des dotierten Übergangsmetalls nur in kristallinen Filmen beobachtet werden. Weiterhin wurde herausgefunden, dass die vom Dotanden hervorgerufenen Sekundärphasen durch die initiale Mikrostruktur unterdrückt werden können. Die experimentellen Ergebnisse wurden mit aktuellen Theorien verglichen. Zusammenfassend wird ein Überblick über die wichtigsten Ergebnisse gegeben, auf Basis welcher eine optimale Mikrostruktur für ein verdünntes magnetisches Oxid vorgeschlagen wird.:1 Introduction 2 1.1 Spintronics 2 1.2 Dilute magnetic oxides 5 2 Fundamentals 13 2.1 Introduction 13 2.2 Magnetism in diluted magnetic oxides 13 2.2.1 Possible locations of dopant 3d ions in an oxide matrix 14 2.2.2 Mean field model 15 2.2.3 Bound magnetic polaron model 16 2.2.4 Charge transfer model 17 2.2.5 Ferromagnetism in undoped oxides 19 2.2.6 Extrinsic sources of ferromagnetism 20 2.3 Motivation 21 3 Experimental 24 3.1 Sample preparation 24 3.1.1 DC magnetron sputtering 24 3.1.2 Ion implantation 27 3.2 X-ray methods 29 3.2.1 X-ray diffraction 29 3.2.2 X-ray absorption 31 3.2.2.1 Synchrotron radiation 31 3.2.2.2 Physics of X-ray absorption 31 3.3 SQUID magnetometry 35 3.3.1 Avoiding magnetic contamination 37 3.4 Positron annihilation spectroscopy 38 4 TM Implantation into Different TiO2 Structures (TM = Co, Mn, V) 43 4.1 Experiments 43 4.2 Co+ implantation: from diluted paramagnetism to superparamagnetic clusters 45 4.2.1 Cluster-free Co+-implanted TiO2 thin films 45 4.2.1.1 Experiments 45 4.2.1.2 Structural properties 46 4.2.1.3 Implantation-induced structural defects 47 4.2.1.4 Magnetic properties 50 4.2.1.5 Local environment of implanted Co atoms 51 4.2.1.6 Summary 52 4.2.2 Revealing nano-clusters within Co+-implanted TiO2 thin films 54 4.2.2.1 Experiments 54 4.2.2.2 Structural properties 54 4.2.2.3 Magnetic properties 57 4.2.2.4 Local environment of implanted Co atoms 59 4.2.2.5 Summary 61 4.3 Mn+ implantation: from a non-magnet to a ferromagnet 63 4.3.1 Experiments 63 4.3.2 Relation between lattice damage and defects 64 4.3.3 Electrical transport properties 65 4.3.4 Local environment of implanted Mn atoms 66 4.3.5 Magnetic properties 67 4.3.6 Summary 69 4.4 V+-implanted TiO2 thin films 71 4.4.1 Experiments 71 4.4.2 Magnetic properties 71 4.4.3 Summary 74 5 The effect of the open volume defects on the magnetic properties of V:TiO2 films prepared by doping during deposition 76 5.1 Experiments 76 5.2 Structural Properties 77 5.3 Investigation of the open volume defects 78 5.4 Magnetic, optical and electrical properties 79 5.5 Summary 81 6 Conclusions 84 6.1 Defects in TiO2 84 6.2 Formation of secondary phases 85 6.3 Evolution of the ferromagnetism in different microstructures of TiO2 87 7 Acknowledgments 9

Nonlinear Processing with Linear Optics

Deep neural networks have achieved remarkable breakthroughs by leveraging multiple layers of data processing to extract hidden representations, albeit at the cost of large electronic computing power. To enhance energy efficiency and speed, the optical implementation of neural networks aims to harness the advantages of optical bandwidth and the energy efficiency of optical interconnections. In the absence of low-power optical nonlinearities, the challenge in the implementation of multilayer optical networks lies in realizing multiple optical layers without resorting to electronic components. In this study, we present a novel framework that uses multiple scattering that is capable of synthesizing programmable linear and nonlinear transformations concurrently at low optical power by leveraging the nonlinear relationship between the scattering potential, represented by data, and the scattered field. Theoretical and experimental investigations show that repeating the data by multiple scattering enables non-linear optical computing at low power continuous wave light.Comment: 20 pages, 9 figures and 1 tabl

Structure and Giant Inverse Magnetocaloric Effect of Epitaxial Ni-Co-Mn-Al Films

The structural, magnetic, and magnetocaloric properties of epitaxial Ni-Co-Mn-Al thin films with different compositions have been studied. The films were deposited on MgO(001) substrates by co-sputtering on heated substrates. All films show a martensitic transformation, where the transformation temperatures are strongly dependent on the composition. The structure of the martensite phase is shown to be 14M. The metamagnetic martensitic transformation occurs from strongly ferromagnetic austenite to weakly magnetic martensite. The structural properties of the films were investigated by atomic force microscopy and temperature dependent X-ray diffraction. Magnetic and magnetocaloric properties were analyzed using temperature dependent and isothermal magnetization measurements. We find that Ni$_{41}$Co$_{10.4}$Mn$_{34.8}$Al$_{13.8}$ films show giant inverse magnetocaloric effects with magnetic entropy change of 17.5\,J\,kg$^{-1}$K$^{-1}$ for $\mu_0 \Delta H=5\,\text{T}$.Comment: 8 pages, 8 figure

Uloga bespilotnih letjelica u praćenju naglih pojava klizišta

This study used an unmanned aerial vehicle (UAV) that was designed and produced to monitor rapidly occurring landslides in forest areas. It aimed to determine the location data for the study area using image sensors integrated into the UAV. The study area was determined as the landslide sites located in the Taşlıçiftlik campus of Gaziosmanpaşa University, Turkey. It was determined that landslide activities were on going in the determined study area and data was collected regarding the displacement of materials. Additionally, it was observed that data about landslides may be collected in a fast and sensitive way using UAVs, and this method is proposed as a new approach. Flights took place over a total of five different periods. In order to determine the direction and coordinate variables for the developed model, eight Ground Control Points (GCPs), whose coordinates were obtained using the GNSS method, were placed on the study area. In each period, approximately 190 photographs were investigated. The photos obtained were analyzed using the Pix4D software. At the end of each period, the Root Mean Square and Ground Sample Distance (GSD) values of the GCPs were calculated. Orthomosaic and digital surface models (DSM) were produced for the location and height model. The results showed that max RMS=±3.3 cm and max GSD=3.57 cm. When the first and fifth periods were compared, the highest spatial displacement value ΔS=111.0 cm, the highest subsidence value Δh=37.3 cm and the highest swelling value Δh=28.6 cm were measured.U ovom radu korištena je bespilotna letjelica (UAV) koja je dizajnirana i proizvedena za potrebe praćenja nagle pojave klizišta u šumskim područjima. Njezin cilj je određivanje podataka o lokaciji područja istraživanja koristeći slikovne senzore ugrađene u UAV. Područje istraživanja je lokacija klizišta u kampusu Taşlıçiftlik Sveučilišta Gaziosmanpaşa, Turska. Utvrđeno je da se klizišta stalno pojavljuju u području istraživanja, a podaci su prikupljeni na temelju pomaka materijala. Osim toga, ustanovljeno je da se podaci o klizištima mogu prikupljati brzo i precizno koristeći UAV, te je ta metoda predložena kao novi pristup. Letovi su obavljeni kroz pet različitih razdoblja. Kako bi se utvrdile varijable smjera i koordinata za razvijeni model, na području istraživanja, postavljeno je osam stalnih točaka (GCP) čije su koordinate dobivene GNSS metodom. U svakom razdoblju proučeno je otprilike 190 fotografija. Dobivene fotografije su analizirane pomoću softvera Pix4D. Na kraju svakog razdoblja izračunate su vrijednosti Root Mean Square (RMS) i Ground Sample Distance (GSD) za GCP. Ortomozaični i digitalni modeli površine (DSM) izrađeni su za lokacijski i visinski model. Rezultati su pokazali da je maksimalni RMS=±3,3 cm, a maksimalni GSD=3,57 cm. Nakon usporedbe prvog i petog razdoblja, izmjerene su najviša vrijednost prostornog pomaka ΔS=111,0 cm, najviša vrijednost slijeganja Δh=37,3 cm i najviša vrijednost ispupčenosti Δh=28,6 cm

Forward-Forward Training of an Optical Neural Network

Neural networks (NN) have demonstrated remarkable capabilities in various tasks, but their computation-intensive nature demands faster and more energy-efficient hardware implementations. Optics-based platforms, using technologies such as silicon photonics and spatial light modulators, offer promising avenues for achieving this goal. However, training multiple trainable layers in tandem with these physical systems poses challenges, as they are difficult to fully characterize and describe with differentiable functions, hindering the use of error backpropagation algorithm. The recently introduced Forward-Forward Algorithm (FFA) eliminates the need for perfect characterization of the learning system and shows promise for efficient training with large numbers of programmable parameters. The FFA does not require backpropagating an error signal to update the weights, rather the weights are updated by only sending information in one direction. The local loss function for each set of trainable weights enables low-power analog hardware implementations without resorting to metaheuristic algorithms or reinforcement learning. In this paper, we present an experiment utilizing multimode nonlinear wave propagation in an optical fiber demonstrating the feasibility of the FFA approach using an optical system. The results show that incorporating optical transforms in multilayer NN architectures trained with the FFA, can lead to performance improvements, even with a relatively small number of trainable weights. The proposed method offers a new path to the challenge of training optical NNs and provides insights into leveraging physical transformations for enhancing NN performance

Endothelial function in patients with familial Mediterranean fever-related amyloidosis and association with cardiovascular events

Objectives. Secondary amyloidosis is the most important complication of FMF and endothelial function is more severely impaired. Elevated asymmetric dimethyl arginine (ADMA) may mediate the excess cardiovascular disease (CVD) risk of this group. We aimed to compare endothelial function characteristics, including ADMA, in patients with FMF-related amyloidosis and primary glomerulopathies and to define risk factors for a CVD event. Methods. We undertook a cross-sectional study with prospective follow-up including consecutive patients with FMF-related amyloidosis (n = 98) or other non-diabetic glomerulopathies (n = 102). All patients had nephrotic-range proteinuria and normal glomerular filtration rate. Flow-mediated dilatation (FMD) was assessedand ADMA levels, CRP and pentraxin 3 (PTX3) were determined. Patients were followed for cardiovascular events. Results. Amyloidosis patients secondary to FMF showed higher levels of ADMA, CRP and PTX3 and lower FMD as compared with patients with other glomerulopathies. Cardiovascular events (n = 54) were registered during 3 years of follow-up. Increased ADMA levels and lower FMD were observed in patients with cardiovascular risk in both groups, but especially in individuals with amyloidosis.Conclusion. Patients with FMF-related amyloidosis have increased CVD event risk, probably related to the high ADMA levels, elevated inflammatory markers and decreased FMD measures observed in these patients

Age- and region-specific hepatitis B prevalence in Turkey estimated using generalized linear mixed models: a systematic review

Toy M, Önder FO, Wörmann T, et al. Age- and region-specific hepatitis B prevalence in Turkey estimated using generalized linear mixed models: a systematic review. BMC infectious diseases. 2011;11(1): 337.BACKGROUND: To provide a clear picture of the current hepatitis B situation, the authors performed a systematic review to estimate the age- and region-specific prevalence of chronic hepatitis B (CHB) in Turkey. METHODS: A total of 339 studies with original data on the prevalence of hepatitis B surface antigen (HBsAg) in Turkey and published between 1999 and 2009 were identified through a search of electronic databases, by reviewing citations, and by writing to authors. After a critical assessment, the authors included 129 studies, divided into categories: 'age-specific'; 'region-specific'; and 'specific population group'. To account for the differences among the studies, a generalized linear mixed model was used to estimate the overall prevalence across all age groups and regions. For specific population groups, the authors calculated the weighted mean prevalence. RESULTS: The estimated overall population prevalence was 4.57, 95% confidence interval (CI): 3.58, 5.76, and the estimated total number of CHB cases was about 3.3 million. The outcomes of the age-specific groups varied from 2.84, (95% CI: 2.60, 3.10) for the 0-14-year olds to 6.36 (95% CI: 5.83, 6.90) in the 25-34-year-old group. CONCLUSION: There are large age-group and regional differences in CHB prevalence in Turkey, where CHB remains a serious health problem

Global disparities in surgeons’ workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study

: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI

Enterprise Architecture Management: A status quo of student processes

Die vorliegende Bachelorarbeit analysiert IT-Prozesse der Hochschule für Angewandte Wissenschaften (HAW) Hamburg, mit denen Studierende in den verschiedenen Einrichtungen in Berührung kommen. Dazu werden u. a. unterschiedliche IT-Anwendungen untersucht, die die Studierendenprozesse unterstützen. Mit Hilfe von Interviews mit den entsprechenden Stakeholdern wird die Ist-Situation der Unternehmensarchitektur erfasst und anschließend werden EAM-Aspekte wie z. B. Redundanzen, Medienbrüche und sogenannte IT-Schattensysteme evaluiert.This bachelor thesis analyses IT processes of the Hamburg University of Applied Sciences, which students come in contact with in the various departments. For that purpose, different IT applications supporting student processes are examined. Based on interviews with the relevant stakeholders, the status quo of the enterprise architecture is captured and subsequently the EAM aspects such as redundancies and media breaks as well as the so-called IT shadow systems are evaluated