| 1. |
- Boikov, Iouri, 1949, et al.
(författare)
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Strain-enhanced phase separation affecting electro- and magnetotransport in La0.67Ca0.33MnO3 films
- 2004
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Ingår i: Journal of Applied Physics. ; 96:1, s. 435-442
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Tidskriftsartikel (refereegranskat)abstract
- Biaxial strain during nucleation influences phase separation into ferromagnetic (metallic) and nonferromagnetic (insulating) regions and that, in turn, markedly affects the electric transport of a manganite film. A 40-nm-thick La0.67Ca0.33MnO3 film, coherently constrained by a (001)LaAlO3 substrate, possesses a noticeably contracted unit cell volume (Veff[approximate]56.70 Å3) as compared with that of a stoichiometric bulk sample. It corresponds to a higher relative concentration (45%) of tetravalent manganese ions in the manganite layer than that in the target (33%). The resistivity rho(T) curve of the strained film peaks twice in the range 4.2300 K. The charge transport of strained La0.67Ca0.33MnO3 films is non-ohmic at T
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| 2. |
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| 3. |
- Brucas, Rimantas, 1965, et al.
(författare)
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Tunneling and charging effects in discontinuous superparamagnetic Ni81Fe19/Al2O3 multilayers
- 2010
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969 .- 1098-0121 .- 1550-235X. ; 81:22, s. 224437-
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic and transport properties of films based on discontinuous layers of Ni81Fe19 (Py) embedded in Al2O3 were investigated. In films with nominal Py thicknesses 6 and 8 angstrom superparamagnetic particles with median diameters D-med = 2.8 and 3.1 nm and distribution widths sigma(D)= 1.2 and 1.3 nm were formed. Current voltage (IU) curves were measured with the current perpendicular to the film plane. The analyses show that the charge transport occurs via tunneling; with the charging energy supplied by thermal fluctuations at high temperature, T >= 100 K, and by the electric field at low temperature, T
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| 4. |
- Demidov, V. V., et al.
(författare)
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Magnetic anisotropy in strained manganite films and bicrystal junctions
- 2013
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 113:16
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Tidskriftsartikel (refereegranskat)abstract
- Transport and magnetic properties of La0.67Sr0.33MnO3 (LSMO) manganite thin films and bicrystal junctions were investigated. Epitaxial manganite films were grown on SrTiO3, LaAlO3, NdGaO3 (NGO), and (LaAlO3)(0.3) + (Sr2AlTaO6)(0.7) substrates, and their magnetic anisotropy were determined by two independent techniques of magnetic resonance spectroscopy. It was demonstrated that by using these techniques, a small (0.3%) anisotropy of crystal structure at the (110) surface plane of the orthorhombic NGO substrate leads to uniaxial magnetic anisotropy of the films in the plane of the substrate at least at the room temperature. It was found that on vicinal NGO substrates, the value of magnetic anisotropy strength can be varied in the range 100-200 Oe at T = 295 K by changing the substrate vicinal angle from 0 degrees to 25 degrees. Measurement of the magnetic anisotropy of manganite bicrystal junction demonstrated the presence of two ferromagnetic spin subsystems for both types of bicrystal boundaries with tilting of basal plane of manganite tilted bicrystal (TB-junction) and with rotation of crystallographic axes (RB-junction) used for comparison. The magnetoresistance of TB-junctions increases with decreasing temperature and the misorientation angle. Variation of bicrystal misorientation angle does not lead to change of misorientation of easy magnetic axes in the film parts forming TB-junction. Analysis of the voltage dependencies of bicrystal junction conductivity show that the low value of the magnetoresistance for the LSMO bicrystal junctions can be caused by two scattering mechanisms. The first one is the spin-flip of spin-polarized carriers due to the strong electron-electron interactions in a disordered layer at the bicrystal boundary at low temperatures and the second one is spin-flip by antiferromagnetic magnons at high temperatures.
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| 5. |
- Gunnarsson, Robert, 1972-, et al.
(författare)
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A phenomenographic analysis of students’ use of base-ten material
- 2020
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Konferensbidrag (refereegranskat)abstract
- Previous research indicates that manipulatives, like base-ten blocks, not necessarily strengthen students’ understanding of numerical place-value and the decimal numeral system. This study takes its starting point in the hypothesis that to create functional teaching situations with base-ten blocks, it is necessary to first know students’ prior understanding of such manipulatives. Therefore, here we present a phenomenographic analysis of students’ understanding how such manipulative material can be used to represent multidigit numbers. The data was collected from individual interviews with 58 students in grade 1 (6-7 years old).We identify six qualitatively different categories of students’ understanding, and, based on these, suggest implications for the design of teaching situations.
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| 6. |
- Gunnarsson, Robert, 1972
(författare)
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Anisotropic spin-orbit interaction revealed by in-plane magnetoresistance in single-oriented SrRuO3 thin films
- 2012
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969 .- 1098-0121 .- 1550-235X. ; 85:23, s. 235409-
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Tidskriftsartikel (refereegranskat)abstract
- A detailed analysis of the in-plane magnetoresistance anisotropy in single orientation thin filmSrRuO3 grown on (001)SrTiO3 is presented. The resistivity is measured in strips along [001], [¯110]and [¯11¯1] with in-plane rotating magnetic field. The data show new details in the transfer fromnegative to positive magnetoresistance when the field is rotated in the plane. They show that themagnetoresistance is anisotropic with respect to the crystalline directions rather than with respectto the direction of the current. The data suggest an
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| 7. |
- Gunnarsson, Robert, 1972-, et al.
(författare)
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Brackets and the structure sense
- 2014
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Ingår i: Development of Mathematics Teaching: Design, Scale, Effects. - Linköping : Svensk förening för MatematikDidaktisk Forskning - SMDF. - 9789197393492 ; , s. 47-55
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Konferensbidrag (refereegranskat)abstract
- Brackets are essential structure elements in mathematics expressions. However, students have shown to have scattered understanding of the concept of brackets and how they are used in mathematical expressions. In this paper we present data that illustrate students’ perceptions of the word “brackets” and how these perceptions influence their use of brackets in numerical expressions. Based on our data we argue that the teaching of the concept of brackets also need to describe brackets as ordered pairs where each symbol has a unique counterpart and that insertion of brackets can, but does not have to, modify the structure of an expression.
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| 8. |
- Gunnarsson, Robert, 1972-
(författare)
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En studie om elevers uppfattning om associativitet och hur det kan påverka algebraundervisningen
- 2022
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Ingår i: The relation between mathematics education research and teachers’ professional development. - Göteborg : Svensk förening för MatematikDidaktisk Forskning - SMDF. - 9789198402452 ; , s. 131-131
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Konferensbidrag (refereegranskat)abstract
- Denna presentation beskriver en pågående studie om hur associativitet kan uppfattas och hanteras i matematikundervisning. Studien syftar till att beskriva elevers olika sätt att förstå associativitet och utifrån dessa designa lämpliga undervisningsinslag för att främja elevernas algebraiska förståelse. Vissa delresultat beskrivs.
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| 9. |
- Gunnarsson, Robert, 1972-, et al.
(författare)
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Evaluation of recipes for obtaining single terminated perovskite oxide substrates
- 2009
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Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 603:1, s. 151-157
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Tidskriftsartikel (refereegranskat)abstract
- We have re-assessed different methods to obtain single terminated perovskite oxide substrate surfaces of SrTiO3, LaAlO3 and NdGaO3. The surfaces have been probed by a combination of atomic and lateral force microscopy, X-ray photoelectron spectroscopy and reflection high-energy electron diffraction. (0 0 1)SrTiO3 surfaces were prepared with HF or plasma etching and annealing, (0 0 1)LaAlO3 surfaces were prepared with or without HCl etching and a consecutive annealing at 750–1100 °C, and (1 1 0)NdGaO3 surfaces were only annealed. Two of the recipes have previously been suggested to result in A-site terminated surfaces. However, except for the case of high-temperature annealed LaAlO3 where we observe a double-terminated surface, our data suggest that the single terminated surfaces obtained by these methods were of B-site type.
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| 10. |
- Gunnarsson, Robert, 1972, et al.
(författare)
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Fabrication and characterisation of La0.67Sr0.33MnO3 submicron grain boundary junctions
- 2004
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Ingår i: Annalen der Physik (Leipzig). ; 13:1-2, s. 101-102
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Konferensbidrag (refereegranskat)abstract
- We have successfully fabricated LSMO grain boundary bicrystaljunctions with widths down to 200 nm. The grain boundaries aresymmetric with misorientation angles of 24degrees or 36.8degrees, and the microbridges are positioned across thosewith a precision better than 0.5 micro-meter. Grain boundary magnetoresistance is observed in the wider junctions but not in the most narrow junction.
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