| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- Gunnarsson, Robert, 1972-, et al.
(författare)
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On the use of emphasizing brackets when learning precedence rules
- 2012
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Ingår i: Evaluation and comparison of mathematical achievement: Dimensions and perspectives. - Linköping : Svensk förening för matematikdidaktisk forskning (SMDF). - 9789197393485 ; , s. 209-210
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Konferensbidrag (refereegranskat)
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| 6. |
- Gunnarsson, Robert, 1972-
(författare)
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The model of the particle nature of matter in science and science education
- 2014
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Konferensbidrag (refereegranskat)abstract
- The model of the particle nature of matter has been one of the fundaments in science and science education. This model describes matter as being composed of small hard solid entities - particles - often known as atoms and molecules, clinging to each other or moving around in empty space. However, from a scientific point of view there are problems with this model; for instance, quantum mechanics describes atoms as having both particle as well as wave properties implying that the entities are neither hard nor solid. The particle nature of matter model is also facing problems within science education. Students’ conceptions of the concept of particle appears to be limited.In this talk I will describe how science teachers’ understanding of the model of the particle nature of matter is limited too. Eleven secondary school science teachers were interviewed about their arguments for the particle nature of matter. Although the teachers appears to have an epistemological understanding of the concept of models in science they give vague arguments for the particle nature of matter model. Particularly, they have problems justifying the model from specific experiments. The model of the particle nature of matter is discussed in the light of these interview data, but also in the light of historical arguments and verifications of the model.
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| 7. |
- Gunnarsson, Robert, 1972-, et al.
(författare)
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Useless brackets in arithmetic expressions with mixed operations
- 2012
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Ingår i: Proceedings of the 36th Conference of the International Group for the Psychology of Mathematics Education. - : The International Group for the Psychology of mathematics Education. ; , s. 2-275-2-282
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Konferensbidrag (refereegranskat)abstract
- There can be different intentions with brackets in mathematical expressions. It has previously been suggested that mathematically useless brackets can be educationally useful when learning the order of operations in expressions with mixed operations. This paper reports how students (12-13 years) deal with the implicit mental conflict between brackets as a necessary part of the order of operations and brackets to emphasize precedence. The students taking part in this quasi-experimental study were instructed on the order of operations, but were also indirectly exposed to different use of brackets. It is concluded that emphasizing brackets impede the transfer from a left-to-right computation strategy to the use of precedence rules.
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| 8. |
- Kalaboukhov, Alexei, 1975, et al.
(författare)
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Electrical and structural properties of ABO3/SrTiO3 interfaces
- 2012
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Ingår i: Materials Research Society Symposium Proceedings. - Warrendale, Pa. : Springer Science and Business Media LLC. - 0272-9172. - 9781605114316 ; 1454, s. 167-172, s. 167-172
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Konferensbidrag (refereegranskat)abstract
- Electrical transport and microstructure of interfaces between nm-thick films of various perovskite oxides grown by pulsed laser deposition (PLD) on TiO2 terminated SrTiO3 (STO) substrates are compared. LaAlO3/STO and KTaO3/STO interfaces become quasi-2DEG after a critical film thickness of 4 unit cell layers. The conductivity survives long anneals in oxygen atmosphere. LaMnO3/STO interfaces remain insulating for all film thicknesses and NdGaO3/STO interfaces are conducting but the conductivity is eliminated after oxygen annealing. Medium-energy ion spectroscopy and scanning transmission electron microscopy detect cationic intermixing within several atomic layers from the interface in all studied interfaces. Our results indicate that the electrical reconstruction in the polar oxide interfaces is a complex combination of different mechanisms, and oxygen vacancies play an important role.
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| 9. |
- Kalaboukhov, Alexei, 1975, et al.
(författare)
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Inhomogeneous Microstructure and Electrical Transport Properties at the LaAlO3/SrTiO3 Interface
- 2012
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Ingår i: Japanese Journal of Applied Physics. - 1347-4065 .- 0021-4922. ; 51:11(spec.issue), s. article no. 11PG10 -
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Tidskriftsartikel (refereegranskat)abstract
- Medium-energy ion spectroscopy (MEIS), scanning transmission electron microscopy (STEM) and X-ray photoemission spectroscopy (XPS) were used to investigate the composition and microstructure of LaAlO3/SrTiO3 (LAO/STO) interfaces grown by pulsed laser deposition of LAO on TiO2-terminated STO substrates under different oxidizing conditions. MEIS and XPS indicated Sr/La and Al/Ti intermixing within several atomic layers at all studied interfaces. XPS and STEM revealed that La diffuses deeper than Al. Analysis of the MEIS data suggests inhomogeneous lateral distribution of the diffused elements. This is further supported by the observation of a large positive magneto-resistance at low temperatures. We discuss the role of lateral inhomogeneities on the formation of the electron gas at the LAO/STO interface.
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| 10. |
- Karlsson, Annasara, et al.
(författare)
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Students' perceptions of brackets
- 2013
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Ingår i: Proceedings of the 37th Conference of the International Group for the Psychology of Mathematics Education, vol. 5. - Kiel, Germany : IGPME. ; , s. 85-
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Konferensbidrag (refereegranskat)
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