Linda Udby - Academia.edu (original) (raw)

Papers by Linda Udby

Journal of Physics: Condensed Matter, Jan 6, 2016

With the goal of elucidating the background of photoinduced ferromagnetism phenomena observed in ... more With the goal of elucidating the background of photoinduced ferromagnetism phenomena observed in the perovskite structured (Pr,Ca) manganites, the low-temperature magnetostructure of the material Pr Ca MnO 0.9 0.1 3 was revised using cold neutron powder diffraction, SQUID magnetometry and ab initio calculations. Particular emphasis was placed on determining the presence of nanoscale magnetic phase separation. Previously published results of a canted A-AFM average ground state were reproduced to a good precision both experimentally and theoretically, and complemented by investigating the effects of an applied magnetic field of 2.7 T on the magnetostructure. Explicit evidence of nanoscale magnetic clusters in the material was obtained based on high-resolution neutron diffractograms. Along with several supporting arguments, we present this finding as a justification for extending the nanoscale magnetic phase separation model of manganites to the material under discussion despite its very low Ca doping level in the context of the model. In the light of the new data, we also conclude that the low temperature magnetic moment of Pr must be ca. 300% larger than previously thought in this material, close to the high spin value of µ 2 B per formula unit.

arXiv (Cornell University), Oct 18, 2004

We use a real-space recursion method to calculate the local density of states (LDOS) within a mod... more We use a real-space recursion method to calculate the local density of states (LDOS) within a model that contains both d-wave superconducting and antiferromagnetic order. We focus on the LDOS in the superconducting phase near single vortices with either normal or antiferromagnetic cores. Furthermore, we study the low-energy quasiparticle structure when magnetic vortices operate as pinning centers for surrounding unidirectional spin density waves (stripes). We calculate the Fourier transformed LDOS and show how the energy dependence of relevant Fourier components can be used to determine the nature of the magnetic field-induced order, and predict field-induced LDOS features that can be tested by future scanning tunneling microscopy (STM) experiments.

Contributions from science education research, 2021

Curriculum texts for science courses change over time as policy changes. Changes occur in particu... more Curriculum texts for science courses change over time as policy changes. Changes occur in particular wordings in official documents and give rise to changes in possible interpretations. Using a recently published methodology, the study from which this paper reports constructed thematic maps of the development of the curriculum for the upper secondary Danish “Basic Science Course”. The analysis integrates qualitative analysis (critical discourse analysis) with quantitative analysis (linguistic network analysis) to identify and characterise themes in official curriculum texts for the course. This chapter provides illustrative examples of the methodology, a discussion of our methodological choices, and the findings of the study. We analysed curricular texts from 2004 (first curriculum text), 2007 (first change), and 2010 (second change). We focused on four emerging themes: Structural Demands, Implementation of Teaching, The Importance of Science in a Bildung Perspective, and BSC’s Identity as a Course. The findings show that Structural Demands changed little over time; the didactical focus remained on “active learning”. Implementation of Teaching first appeared as a theme in 2007 and matured in 2010 to be linked to the identity of the course as well as the goals for competences to be learned. Finally, we found that The Importance of Science in a Building Perspective started out as a separate theme but merged in 2010 to become integral to the purpose of the Basic Science Course. This may signify a maturation of the course to represent a school discipline in its own right. It may also imply an official intention that science should be part of most students’ development as citizens. The chapter discusses the appropriateness of thematic maps as analytical tools and how these curricular analyses can be linked to the political discussions amongst stakeholders.

APS, Mar 1, 2009

Previous work by our group has determined that the low temperature phase diagram of super-oxygena... more Previous work by our group has determined that the low temperature phase diagram of super-oxygenated, La2CuO4 consists of only a few line phases that are either superconducting (SC) or magnetic. Samples with doping levels between the stable phases will segregate into separate domains; this raises the question as to the nature of the interaction between SC and magnetic domains. The

This is image documentation of our test-version of the web-app that is used in the game. https://... more This is image documentation of our test-version of the web-app that is used in the game. https://cgl-marsbasen-test.web.app/ (Upon release of the final app, this test-version will become void). <strong>Marsbasen is a learning game aimed at high schools, which is specifically developed to teach C-level physics curriculum. In the learning game, students take on the role of a team of pioneers, who are sent to Mars to establish a base. Naturally, this involves a series of scientific challenges, which means that the students must acquire new knowledge, and put that knowledge to good use.</strong> Marsbasen is framed by an interactive and partially digital story. Teaching takes place both digitally, in the classroom and doing experiments in the lab. The students experience the game as a progressive story, which they are able to influence. Meanwhile, the goal is to learn physics at C-level.

Contributions from Science Education Research, 2021

Tidsskriftet Læring og Medier (LOM), 2016

Dansk resumé Vi beskriver, hvordan virtuelle eksperimenter kan udnyttes i et laeringsdesign ved a... more Dansk resumé Vi beskriver, hvordan virtuelle eksperimenter kan udnyttes i et laeringsdesign ved at forberede de studerende til hands-on-eksperimenter ved storskalafaciliteter. Vi illustrerer designet ved at vise, hvordan virtuelle eksperimenter bruges på Niels Bohr Institutets kandidatkursus om neutronspredning. I den sidste uge af kurset, rejser studerende til et storskala neutronspredningsfacilitet for at udføre neutronspredningseksperimenter. Vi bruger studerendes udsagn om deres oplevelser til at argumentere for, at arbejdet med virtuelle experimenter forbereder de studerende til at engagere sig mere frugtbart med eksperimenter ved at lade dem fokusere på fysikken og relevante data i stedet for instrumenternes funktion. Vi haevder, at det er, fordi de kan overføre deres erfaringer med virtuelle eksperimenter til rigtige eksperimenter. Vi finder dog, at laering stadig er situeret i den forstand, at kun kendskab til bestemte eksperimenter overføres. Vi afslutter med at diskutere de muligheder, som virtuelle eksperimenter giver.

Journal of Physics: Condensed Matter, 2016

We studied oxygen staging in a series of La2-xSrxCuO4 (LSCO) samples using neutron scattering. Th... more We studied oxygen staging in a series of La2-xSrxCuO4 (LSCO) samples using neutron scattering. The samples were oxidized using electrochemistry. Electronic phase separation was previously reported in the oxygen rich LSCO system with two stable phases identified as optimally doped superconducting phase and a magnetic phase (1/8th like) with the same ordering temperatures at 40 K [1]. Our present studies show staging in this system. Although staging was observed and extensively studied in the samples with no Sr [2], it has not been reported or systematically studied in the systems with both Sr and oxygen. We do find staging in the oxygenated LSCO system, but the staging peaks evolve as Sr concentration increases and excess oxygen concentration decreases. [1] H Mohottala et al. Nature Materials 5, 377-382 (2006), [2] B.O. Wells et al., Z. Phys. B 100, 535 (1996).

Inelastic neutron scattering has been used to study the in-plane Cu-O bond-stretching mode in oxy... more Inelastic neutron scattering has been used to study the in-plane Cu-O bond-stretching mode in oxygen doped La_1.94Sr_0.06CuO_4.035 (T_c = 38 K) and La_2CuO_4+δ (T_c = 43 K). Similar to results from optimally doped La_1.85Sr_0.15CuO_4 (T_c = 35 K), we observe anomalous features in the dispersion of this half-breathing mode in the form of a softening halfway through the Brillouin Zone. Considering the differences in electronic structure and local environment between the oxygen- and strontium-doped compounds with similar T_c, we rule out a connection between the phonon anomaly and structural instabilities related to the specific dopant type. We interpret the phonon anomaly as a signature of correlated charge fluctuations possibly connected to stripes.

Surface Science, 2002

Synchrotron-radiation-induced photoelectron spectroscopy (SRPES) has been used to investigate the... more Synchrotron-radiation-induced photoelectron spectroscopy (SRPES) has been used to investigate the reaction of NO 2 over vanadia thin films at different coverages on TiO 2 (1 1 0)-1 Â 1. The stoichiometry and structure of the vanadia films are controlled to be VO 2 , rutile structured, using a previously published non-dioxygen-ambient method of synthesis in UHV. The reactivity of these VO 2 films towards NO 2 varies with their coverages. The results are interpreted with regard to the surface structure and stoichiometry.