Emergence of ferroelectricity at the morphotropic phase boundary of ultrathin BiFeO3_3

We demonstrate the robustness of polarization in ultrathin compressive strained BiFeO$_3$ single layers and heterostructures during epitaxial thin-film growth. Using in-situ optical second harmonic generation (ISHG), we explore the emergence of ferroelectric phases at the strain-driven morphotropic phase boundary in the ultrathin regime. We find that the epitaxial films grow in the ferroelectric tetragonal (T-) phase without exhibition of a critical thickness. The robustness of this high-temperature T-phase against depolarizing-field effects is further demonstrated during the growth of capacitor-like (metal|ferroelectric|metal) heterostructures. Using temperature-dependent ISHG post-deposition, we identify the thickness-dependent onset of the monoclinic distortion in the T-matrix and trace the signature of the subsequent emergence of the strain-relaxed rhombohedral-like monoclinic phase. Our results show that strain-driven T-phase stabilization in BiFeO$_3$ yields a prominent candidate material for realizing ultrathin ferroelectric devices.Comment: 5 pages, 3 figure

Epitaxy of hexagonal ABO3_3 quantum materials

Hexagonal $AB$O$_3$ oxides ($A$, $B$ = cation) are a rich materials class for realizing novel quantum phenomena. Their hexagonal symmetry, oxygen trigonal bipyramid coordination and quasi-two dimensional layering give rise to properties distinct from those of the cubic $AB$O$_3$ perovskites. As bulk materials, most of the focus in this materials class has been on the rare earth manganites, $R$MnO$_3$ ($R$ = rare earth); these materials display coupled ferroelectricity and antiferromagnetic order. In this review, we focus on the thin film manifestations of the hexagonal $AB$O$_3$ oxides. We cover the stability of the hexagonal oxides and substrates which can be used to template the hexagonal structure. We show how the thin film geometry not only allows for further tuning of the bulk-stable manganites but also the realization of metastable hexagonal oxides such as the $R$FeO$_3$ that combine ferroelectricity with weak ferromagnetic order. The thin film geometry is a promising platform to stabilize additional metastable hexagonal oxides to search for predicted high-temperature superconductivity and topological phases in this materials class.Comment: The following article has been accepted by Applied Physics Review

Aktieägarnas betydelse- En studie av ersättningssystemens utformning i noterade bolag

Uppsatsens syfte är att undersöka hur ägarinflytande, i form av ägarkoncentration och ägartyp i ett företag, påverkar det monetära ersättningssystemets utformning till företagets verkställande direktör i svenska noterade bolag. Detta har skett genom en kvantitativ studie, där sekundära källor i form av årsredovisningar har studerats. Utifrån datan har statistiska tester utförts, för att undersöka olika samband mellan ägarkoncentration, ägartyp och ersättningssystemens utformning. Resultaten som har konstaterats visar att ägande, i form av ägarkoncentration och en viss typ av ägandeskap, har betydelse för ersättningens sammansättning. Företag med hög ägarkoncentration använder sig av färre ersättningskomponenter, medan företag med låg ägarkoncentration har ett ersättningssystem som innehåller fler komponenter. Vidare kan ett samband mellan ett passivt ägandeskap och fler ersättningskomponenter konstateras

Fecal luminal factors from patients with irritable bowel syndrome induce distinct gene expression of colonoids

Background: Alteration of the host-microbiota cross talk at the intestinal barrier may participate in the pathophysiology of irritable bowel syndrome (IBS). Therefore, we aimed to determine effects of fecal luminal factors from IBS patients on the colonic epithelium using colonoids. Methods: Colon-derived organoid monolayers, colonoids, generated from a healthy subject, underwent stimulation with fecal supernatants from healthy subjects and IBS patients with predominant diarrhea, phosphate-buffered saline (PBS), or lipopolysaccharide (LPS). Cytokines in cell cultures and fecal LPS were measured by ELISA and mRNA gene expression of monolayers was analyzed using Qiagen RT2 Profiler PCR Arrays. The fecal microbiota profile was determined by the GA-map™ dysbiosis test and the fecal metabolite profile was analyzed by untargeted liquid chromatography/mass spectrometry. Key results: Colonoid monolayers stimulated with fecal supernatants from healthy subjects (n\ua0=\ua07), PBS (n\ua0=\ua04) or LPS (n\ua0=\ua03) presented distinct gene expression profiles, with some overlap (R2Y\ua0=\ua00.70, Q2=\ua00.43). Addition of fecal supernatants from healthy subjects and IBS patients (n\ua0=\ua09) gave rise to different gene expression profiles of the colonoid monolayers (R2Y\ua0=\ua00.79, Q2=\ua00.64). Genes (n\ua0=\ua022) related to immune response (CD1D, TLR5) and barrier integrity (CLDN15, DSC2) contributed to the separation. Levels of proinflammatory cytokines in colonoid monolayer cultures were comparable when stimulated with fecal supernatants from either donor types. Fecal microbiota and metabolite profiles, but not LPS content, differed between the study groups. Conclusions: Fecal luminal factors from IBS patients induce a distinct colonic epithelial gene expression, potentially reflecting the disease pathophysiology. The culture of colonoids from healthy subjects with fecal supernatants from IBS patients may facilitate the exploration of IBS related intestinal micro-environmental and barrier interactions

Nonlinear optical diode effect in a magnetic Weyl semimetal

Weyl semimetals have emerged as a promising quantum material system to discover novel electrical and optical phenomena, due to their combination of nontrivial quantum geometry and strong symmetry breaking. One crucial class of such novel transport phenomena is the diode effect, which is of great interest for both fundamental physics and modern technologies. In the electrical regime, giant electrical diode effect (the nonreciprocal transport) has been observed in Weyl systems. In the optical regime, novel optical diode effects have been theoretically considered but never probed experimentally. Here, we report the observation of the nonlinear optical diode effect (NODE) in the magnetic Weyl semimetal CeAlSi, where the magnetic state of CeAlSi introduces a pronounced directionality in the nonlinear optical second-harmonic generation (SHG). By physically reversing the beam path, we show that the measured SHG intensity can change by at least a factor of six between forward and backward propagation over a wide bandwidth exceeding 250 meV. Supported by density-functional theory calculations, we establish the linearly dispersive bands emerging from Weyl nodes as the origin of the extreme bandwidth. Intriguingly, the NODE directionality is directly controlled by the direction of magnetization. By utilizing the electronically conductive semimetallic nature of CeAlSi, we demonstrate current-induced magnetization switching and thus electrical control of the NODE in a mesoscopic spintronic device structure with current densities as small as 5 kA/cm$^2$. Our results advance ongoing research to identify novel nonlinear optical/transport phenomena in magnetic topological materials. The NODE also provides a way to measure the phase of nonlinear optical susceptibilities and further opens new pathways for the unidirectional manipulation of light such as electrically controlled optical isolators.Comment: 28 pages, 12 figure

Antiferromagnetic metal phase in an electron-doped rare-earth nickelate

Long viewed as passive elements, antiferromagnetic materials have emerged as promising candidates for spintronic devices due to their insensitivity to external fields and potential for high-speed switching. Recent work exploiting spin and orbital effects has identified ways to electrically control and probe the spins in metallic antiferromagnets, especially in noncollinear or noncentrosymmetric spin structures. The rare earth nickelate NdNiO3 is known to be a noncollinear antiferromagnet where the onset of antiferromagnetic ordering is concomitant with a transition to an insulating state. Here, we find that for low electron doping, the magnetic order on the nickel site is preserved while electronically a new metallic phase is induced. We show that this metallic phase has a Fermi surface that is mostly gapped by an electronic reconstruction driven by the bond disproportionation. Furthermore, we demonstrate the ability to write to and read from the spin structure via a large zero-field planar Hall effect. Our results expand the already rich phase diagram of the rare-earth nickelates and may enable spintronics applications in this family of correlated oxides.Comment: 25 pages, 4 figure

Probing Ferroic States in Oxide Thin Films Using Optical Second Harmonic Generation

Forthcoming low-energy consumption oxide electronics rely on the deterministic control of ferroelectric and multiferroic domain states at the nanoscale. In this review, we address the recent progress in the field of investigation of ferroic order in thin films and heterostructures, with a focus on non-invasive optical second harmonic generation (SHG). For more than 50 years, SHG has served as an established technique for probing ferroic order in bulk materials. Here, we will survey the specific new aspects introduced to SHG investigation of ferroelectrics and multiferroics by working with thin film structures. We show how SHG can probe complex ferroic domain patterns non-invasively and even if the lateral domain size is below the optical resolution limit or buried beneath an otherwise impenetrable cap layer. We emphasize the potential of SHG to distinguish contributions from individual (multi-) ferroic films or interfaces buried in a device or multilayer architecture. Special attention is given to monitoring switching events in buried ferroic domain- and domain-wall distributions by SHG, thus opening new avenues towards the determination of the domain dynamics. Another aspect studied by SHG is the role of strain. We will finally show that by integrating SHG into the ongoing thin film deposition process, we can monitor the emergence of ferroic order and properties in situ, while they emerge during growth. Our review closes with an outlook, emphasizing the present underrepresentation of ferroic switching dynamics in the study of ferroic oxide heterostructures

Experiences of patient participation before care visits among children and youths with Juvenile idiopathic arthritis

Sammanfattning: Introduktion: Juvenil idiopatisk artrit (JIA) är den vanligaste förekommande reumatologiska diagnosen bland barn och unga. Föräldrar styr främst vårdinsatserna, trots att barn och unga med JIA känner sin fysiska och psykiska smärta bäst. Syfte: Syftet med studien är att belysa upplevelser av förberedelser inför vårdbesök bland barn och unga med JIA samt deras föräldrar. Metod: Studien använde sig av en kvalitativ studiedesign. Tio workshop-träffar genomfördes med barn och unga med JIA samt med deras föräldrar. En individuell intervju genomfördes med en ung vuxen. Workshop-träffarna samt den individuella intervjun utgick från en semistrukturerad intervjuguide. Data analyserades med hjälp av Kvalitativ innehållsanalys enligt Graneheim och Lundman, utifrån en induktiv ansats. Resultat: Temat Präglas av barns och ungas mentala processer och värderingar utgör studiens resultat. Temat baseras på tre kategorier samt åtta subkategorier. Förberedelserna inför vårdbesök präglades av barnens och de ungas förhållningssätt till JIA. Somliga barn och unga undanhöll information om deras fysiska och psykiska smärta vid förberedelserna inför vårdbesök. Därför betonades vikten av att fånga upp dessa besvär. De barn och unga som utvecklade goda förhållningssätt till sjukdomstillståndet ökade förutsättningar för att förbereda sig inför vårdbesök, eftersom de då delade med sig av sina upplevelser. Slutsats: Det är viktigt att fånga upp barn och unga med JIA samt deras fysiska och psykiska smärta inför vårdbesök. Tillgodoses upplevelserna, kan förutsättningar för individanpassade vård- och rehabilteringsinsatser skapas. Goda förhållningssätt till JIA främjar förberedelserna inför vårdbesök samt fysiskt och psykiskt välbefinnande bland barn och unga med JIA.Introduction: Juvenile idiopathic arthritis (JIA) is the most common rheumatologic disease among children and youths.  Even if the children and youths with JIA are conscious about their physical and mental health, the parents control their healthcare. Aims: The aim of this study is to investigate experiences of preparations before care visits among children and youths with JIA and their parents.  Methods: The study had a qualitative design, with an inductive approach. Ten workshops were conducted together with children and youths with JIA and their parents. An individual interview was conducted with a young adult. A semi structured interview guide was used. Data was analyzed with Qualitative content analysis according to Graneheim and Lundman. Results: The theme Characterized by the children's and youth's mentally processes and values constitutes the result of the study, and is based on three categories and eight subcategories. Preparations before care visits were characterized by the children's and youth's approach to JIA. Children and youths withheld information about their physical and mental health. The importance of capturing these problems emphasized. Strategies for managing JIA had a positive effect of the preparations before the care visits, because the children and youths were telling about their experiences.  Conclusion: It is necessary to capture the physical and mental health among children and youths with JIA before care visits. This may also form an individualized healthcare and create a better physical and mental health among the group with JIA

Complex polar states in ultrathin epitaxial oxides

The diverse functional properties of transition-metal oxides have given rise to entire fields of research spanning fundamental aspects such as quantum phenomena to the highly applied field of oxide electronics. In the latter, electrically ordered oxides, such as ferroelectrics, stand out as prominent materials for implementation in low-energy-consuming oxide applications due to their characteristic response under the application of mechanical stress, electric field or optical irradiation. The significant progress in oxide thin-film engineering over the last 20 years has enabled studies of such oxide functionality to go beyond bulk crystals and include characterization under confinement of the materials to the nanoscale. However, in epitaxially grown ultrathin films, the manifestation of electric polarization specifically and functionality in general can greatly differ from the behavior of the corresponding bulk crystals. In order to make use of the exotic functionality of ultrathin oxide films, it is therefore essential to understand when and how the polar states are set with respect to the thin-film synthesis and, upon implementation in electronic devices, with respect to device operation. This is however a challenging task. So far, detailed understanding of the ultrathin limit of polarity in oxide thin films remains restricted to a few model systems. In this thesis, we present an approach to probe such polar states in ultrathin oxide layers with high sensitivity and in a nondestructive manner by nonlinear optics. We demonstrate the of use optical second harmonic generation both in situ, during thin-film synthesis, and operando, during device operation, to provide unique insight into the evolution of polar states in oxide films in these highly dynamic environments. Here, we focus on a set of oxide materials whose polar architecture becomes particularly involved in the nanometer limit. We first establish the sensitivity of our optical probe to distinguish between differently oriented polar states with a complex nanoscale microstructure in a single-phase material, and its evolution under electric-field application. We next exploit this sensitivity to follow the phase coexistence of emergent polar phases in an epitaxially strained system during the thin-film synthesis process. We thus obtain novel insight into an unusually robust, yet metastable high-temperature polar phase. We further investigate the peculiar coupling between polarization and structural order in a so-called improper ferroelectric in the ultrathin regime. Here, a combination of nonlinear optics and electron microscopy could reveal the crucial impact of epitaxial interfaces on the evolution of polarization. Finally, we reveal emergent symmetry-breaking in layered oxides during epitaxial growth, allowing the nanoscale design of symmetry and functionality beyond polar compounds. Common to all of these systems, we find that the mechanical and electrostatic boundary conditions set during the thin-film synthesis itself dictates the emergence of electric polarity in the oxide films, which can even result in the emergence of new material phases that are unique to the thin-film geometry and do not have a bulk counterpart. The results presented in this thesis hence point to the many possibilities of designing ultrathin oxides with unique, yet robust, polar properties of interest for both oxide electronics applications and the emergent field of thin-film quantum materials

Upplevelser av delaktighet inför vårdbesök bland barn och unga med Juvenil idiopatisk artrit

Sammanfattning: Introduktion: Juvenil idiopatisk artrit (JIA) är den vanligaste förekommande reumatologiska diagnosen bland barn och unga. Föräldrar styr främst vårdinsatserna, trots att barn och unga med JIA känner sin fysiska och psykiska smärta bäst. Syfte: Syftet med studien är att belysa upplevelser av förberedelser inför vårdbesök bland barn och unga med JIA samt deras föräldrar. Metod: Studien använde sig av en kvalitativ studiedesign. Tio workshop-träffar genomfördes med barn och unga med JIA samt med deras föräldrar. En individuell intervju genomfördes med en ung vuxen. Workshop-träffarna samt den individuella intervjun utgick från en semistrukturerad intervjuguide. Data analyserades med hjälp av Kvalitativ innehållsanalys enligt Graneheim och Lundman, utifrån en induktiv ansats. Resultat: Temat Präglas av barns och ungas mentala processer och värderingar utgör studiens resultat. Temat baseras på tre kategorier samt åtta subkategorier. Förberedelserna inför vårdbesök präglades av barnens och de ungas förhållningssätt till JIA. Somliga barn och unga undanhöll information om deras fysiska och psykiska smärta vid förberedelserna inför vårdbesök. Därför betonades vikten av att fånga upp dessa besvär. De barn och unga som utvecklade goda förhållningssätt till sjukdomstillståndet ökade förutsättningar för att förbereda sig inför vårdbesök, eftersom de då delade med sig av sina upplevelser.  Slutsats: Det är viktigt att fånga upp barn och unga med JIA samt deras fysiska och psykiska smärta inför vårdbesök. Tillgodoses upplevelserna, kan förutsättningar för individanpassade vård- och rehabilteringsinsatser skapas. Goda förhållningssätt till JIA främjar förberedelserna inför vårdbesök samt fysiskt och psykiskt välbefinnande bland barn och unga med JIA