Magnetoelectric Coupling in BaTiO3-BiFeO3 Multilayers: Growth Optimization and Characterization

The presented thesis explores the magnetoelectric (ME) coupling in multiferroic thin film multilayers of BaTiO3 (BTO) and BiFeO3 (BFO). Multiferroics possess more than one ferroic order parameter, in this case ferroelectricity and anti-ferromagnetism. Cross-coupling between these otherwise separate order parameters promises great advantages in the fields of multistate memory, spintronics and even medical applications. The first major challenge in this field of study is the rarity of multiferroics. Second, most known multiferroics, both intrinsic and extrinsic in nature, possess very low ME coupling coefficients. In previous studies conducted by our group, BTO-BFO multilayers deposited by pulsed laser deposition (PLD) showed a ME coupling coefficient αME enhanced by one order of magnitude, when compared to single-layers of the intrinsic multiferroic BFO. However, the mechanism of ME coupling in such heterostructures is poorly understood until now. In this thesis, we used a selection of structural, chemical, electrical and magnetic measurements to maximize the αME-coefficient and shed light on the origin of this enhanced ME effect. The comparison of BTO-BFO multilayers over single-layers revealed not only enhanced ME-coupling, but also reduced mosaicity, roughness and leakage current density in multilayers. Following a parametric sample optimization, we achieved an atomically smooth interface roughness and vast improvements in the ferroelectric properties by introducing a shadow mask in the PLD process. We measured the highest αME-value so far of 480 Vcm-1Oe-1 for a multilayer with a double-layer thickness of only 4.6 nm, two orders of magnitude larger than the coefficient of 4 Vcm-1Oe-1 measured for BFO single-layers. The αME-coefficient in these multilayers stands in an inverse correlation with the double-layer thickness ddl. The influence of oxygen pressure during growth and BTO-BFO ratio on αME was shown to be neglible in comparison to that of ddl. From the characteristic dependencies of αME on magnetic bias field, temperature and ddl, we concluded the existence of an interface-driven coupling mechanism in BTO-BFO multilayers.:1 Introduction 2 Theory of Multiferroic Magnetoelectrics 2.1 Primary Ferroic Properties 2.2 Magnetoelectric Coupling 3 Materials 3.1 The General Structure of Perovskites ABX3 3.2 Strontium Titanate SrTiO3 3.3 Barium Titanate BaTiO3 3.4 Bismuth Ferrite BiFeO3 3.5 Heterostructures Based on BiFeO3 4 Experimental Section 4.1 Thin Film Fabrication 4.2 X–Ray Diffraction 4.3 Microscopic Techniques 4.4 Chemical Analysis Techniques 4.5 Ferroelectric Characterization 4.6 Magnetic Property Measurements 4.7 Measurement of the Magnetoelectric Coupling Coefficient 5 BaTiO3–BiFeO3 Heterostructures 5.1 General Properties of Single-Layers and Multilayers of BTO and BFO 5.2 PLD–Growth of BaTiO3–BiFeO3 Multilayers 5.3 Manipulation of Multilayer Properties through Design 5.4 Effectiveness of Eclipse–PLD 5.5 Enhanced ME Effect in BaTiO3–BiFeO3 Multilayers 6 Summary and Outlook A Magnetoelectric Measurement Setup B Magnetic Background Measurements C Polarized Neutron Reflectometry Literature Own and Contributed Work Acknowledgement Erratu

On the composition of parallel versions of the story "The appearance of the liṅga” (liṅgodbhava) in the Purāṇas

Parallel versions of Purāṇic narratives have been analysed by using text-historical and text-critical methods as well as structural approaches. Less attention has been given to the narrative structures and the ways in which parallel versions are produced. In this regard a narratological approach provides a helpful addition to the other methods. The plot or fabula of the story "The appearance of the liṅga”, which is retold several times in the Purāṇas, can be analysed as consisting of a common, stable set of fabula-elements, which is discernible in each version. Furthermore, the fabula-elements are composed of different text types, namely, doctrinal, prescriptive and liturgical. Differences in the versions can be detected in changes that occur not in all, but usually in only one or two fabula-elements. These differences between the versions are produced by changing events in the narrative as well as including different text types in individual fabula-elements. The combination of different text types is not necessarily an indicator that the narrative is composed of diverse textual layers, at different historical periods or by different authors. Rather, it is a characteristic feature of producing different versions of a narrative for different purposes and in various historical contexts. Furthermore, the combination of text types lends the narrative authority with respect to their doctrinal, normative or ritual conten

Investigation of a Method to Increase the Sensitivity of Counter-Current Immunoelectrophoresis Using Direct-Contact Photography

Counter-current Immunoelectrophoresis (CIE) has been used to detect bacterial capsular polysaccharides in both cerebrospinal fluids and blood serum of children with systemic meningococcal diseases. The sensitivity of the method depends upon the titre of the antisera. It was found that the sensitivity of CIE could not be increased by the method of direct-contact ultraviolet photography. The sensitivity could be increased by one serial dilution, on the average, by the treatment of a 0.25% tannic acid wash for 15 minutes

The dynamics of strong laser-driven shocks in cluster media

Shocks and blast waves are ubiquitous features observed in plasma physics and in astrophysical phenomena and, as such, have long been the subject of experimental and theoretical studies. This thesis describes experimental and numerical investigations of the dynamics of laser driven shocks in cluster media. Target gases of atomic clusters have been shown to exhibit e cient absorption of high-intensity laser radiation, allowing to use `table-top' scale laser systems to drive high Mach-number shock waves. By applying hydrodynamic scaling laws, these systems can provide insight into the physics governing much larger astrophysical phenomena, such as supernova remnants. Experiments were conducted to investigate the structure and propagation dynamics of cylindrical blast waves in radiative and non-radiative gases. Shock pro ling studies performed at Imperial College London are presented, that highlight the need for non-LTE calculations of the shock physics. Investigations into the onset of the radiation driven thermal cooling instability (TCI) were performed by means of a streaked Schlieren technique, developed to obtain single-shot shock trajectory measurements, while removing any ambiguities imposed by shot-to-shot uctuations. In order to scale previous results to higher drive energies, experiments were performed using the Vulcan laser facility at the Rutherford Appleton Laboratory. The resulting cluster absorption and shocked gas comparison data is discussed in detail, including data indicating the rst experimental observation of TCI. To study shock collisions, a unique focal geometry has been employed, creating two near-parallel cylindrical shocks. By means of an interferometric tomography technique, the full 3D electron density pro le was reconstructed, showing complex material transport and Mach stem formation at the oblique shock collision interface, con rmed by 3D hydrodynamics simulations. To investigate this feature further, shock interactions with an obstruction were also performed, showing interesting propagation features through density steps imposed by the obstruction in the cold gas stream

Thymoma and Thymic Carcinoma: Molecular Pathology and Targeted Therapy

Abstract:Thymomas and thymic carcinomas (TC) are rare epithelial tumors of the thymus. Although most thymomas have organotypic features (i.e., resemble the normal thymus), TC are morphologically undistinguishable from carcinomas in other organs. Apart from their different morphology, TC and thymomas differ also in functional terms (TC, in contrast to thymomas, have lost the capacity to promote the maturation of intratumorous lymphocytes), have different genetic features (discussed in this review), a different immunoprofile (most TC overexpress c-KIT, whereas thymomas are consistently negative), and different clinical features (TC, in contrast to thymomas, are not associated with paraneoplastic myasthenia gravis). Thus, although all the data suggest that the biology of thymomas and TC is different, in clinical practice, their therapeutic management up to now is identical. In the age of personalized medicine, the time may have come to think this over. We will briefly review the molecular genetics of malignant thymic tumors, summarize the current status of targeted therapies with an emphasis on the multitargeted kinase inhibitors sunitinib and sorafenib, and try to outline some future directions

Transferring Human Factors Knowledge from Aviation to Development of a Warning System for Landslide

There is a successful history of transferring knowledge from aviation to other domains such as medicine (Thomas & Helmreich, 2002). In this study the ICAO multistage alerting service (2008) served as model for the specification of an early warning system for landslide. The early warning system is designed to monitor mass-movement data provided by GPS sensors, and to generate warnings and alarms to the National Alarm- and Warning Center of Styria, Austria. For the human factors specification of the new system a qualitative analysis was performed. Results are discussed with regard to applicability of human factors guidelines from aviation to development of systems for regional alarming centers which initiate and supervise disaster management activities

Preschool children's use of perceptual-motor knowledge and hierarchical representational skills for tool making

Although other animals can make simple tools, the expanded and complex material culture of humans is unprecedented in the animal kingdom. Tool making is a slow and late-developing ability in humans, and preschool children find making tools to solve problems very challenging. This difficulty in tool making might be related to the lack of familiarity with the tools and may be overcome by children's long term perceptual-motor knowledge. Thus, in this study, the effect of tool familiarity on tool making was investigated with a task in which 5-to-6-yearold children (n = 75) were asked to remove a small bucket from a vertical tube. The results show that children are better at tool making if the tool and its relation to the task are familiar to them (e.g., soda straw). Moreover, we also replicated the finding that hierarchical complexity and tool making were significantly related. Results are discussed in light of the ideomotor approach

Transferring Human Factors Knowledge from Aviation to Development of a Warning System for Landslide

There is a successful history of transferring knowledge from aviation to other domains such as medicine (Thomas & Helmreich, 2002). In this study the ICAO multistage alerting service (2008) served as model for the specification of an early warning system for landslide. The early warning system is designed to monitor mass-movement data provided by GPS sensors, and to generate warnings and alarms to the National Alarm- and Warning Center of Styria, Austria. For the human factors specification of the new system a qualitative analysis was performed. Results are discussed with regard to applicability of human factors guidelines from aviation to development of systems for regional alarming centers which initiate and supervise disaster management activities