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| 2. |
- 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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| 4. |
- Gunnarsson, Robert, 1972, et al.
(författare)
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Magnetization reversal processes in magnetic bicrystal junctions
- 2006
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Ingår i: Phys. Rev. B. ; 73, s. 014435-
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Tidskriftsartikel (refereegranskat)abstract
- We provide experimental data for the magnetoresistance in epitaxial ferromagnetic manganite (La0.7Sr0.3MnO3) bicrystals with various angles. Experiments were conducted using samples with in-plane magnetization as well as with out-of-plane magnetization. The magnetoresistance hysteresis is interpreted directly into different magnetization reversal processes. We show that it is possible to set the electrode magnetization at remanence such that the spins at the bicrystal interface are either parallel or inclined to each other at an angle determined by the crystal orientations. Finally, we demonstrate the feasibility of using epitaxial magnetic bicrystals to probe the transport properties in magnetic junctions with well-determined angles of magnetization.
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| 5. |
- Gunnarsson, Robert, 1972, et al.
(författare)
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Magnetoresistance in bicrystal grain-boundary junctions analyzed within the Stoner-Wohlfarth model
- 2005
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 290-291:part 1, s. 761-763
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Tidskriftsartikel (refereegranskat)abstract
- Experimental data of bicrystal grain boundary magnetoresistance hysteresis shows that the resistance at remanence after saturation depends on whether the magnetic field was applied parallel or perpendicular to the grain boundary. In the latter case the behaviour can be described by the Stoner-Wohlfarth magnetization reversal model for coherent rotation of the magnetization, which leads to an alignment along the easy magnetization directions of the bicrystal in zero field. In the parallel configuration themagnetization directions of the two grains remain parallel in zero field. We have used this information to deduce an effective spin-polarization of P ~ 40 % of the grain boundary in a bicrystal of La0.7Sr0.3MnO3.
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| 6. |
- Kalaboukhov, Alexei, 1975, et al.
(författare)
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Cationic Disorder and Phase Segregation in LaAlO3/SrTiO3 Heterointerfaces Evidenced by Medium-Energy Ion Spectroscopy
- 2009
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 103:14, s. 146101-
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Tidskriftsartikel (refereegranskat)abstract
- Medium-energy ion spectroscopy (MEIS) has been used to study the depth profile and deduce the distribution of possible cationic substitutions in LaAlO3/SrTiO3 (LAO/STO) heterointerfaces. Analysis of La and Sr peaks in aligned and random MEIS spectra indicates that the surface layers of LAO on an STO substrate are not homogeneous and stoichiometric if the film thickness is less than 4 unit cell layers. This is possibly caused by a redistribution of La and Sr at the interface. Kelvin probe force microscopy reveals an inhomogeneous distribution of the surface potential in a 4 unit cell LAO film, indicating micrometer-sized regions of different compositions. Our findings provide a novel view on the microstructural origin of the electrically conductive interfaces.
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| 7. |
- Kalaboukhov, Alexei, 1975, et al.
(författare)
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Effect of oxygen vacancies in the SrTiO3 substrate on the electrical properties of the LaAlO3/SrTiO3 interface
- 2007
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 75:12, s. 121404(R)-
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally investigated optical, electrical, and microstructural properties of heterointerfaces between two thin-film perovskite insulating materials, SrTiO3 (STO) and LaAlO3 (LAO), deposited at different oxygen pressure conditions. Cathode and photoluminescence experiments show that oxygen vacancies are formed in the bulk STO substrate during the growth of LAO films, resulting in high electrical conductivity and mobility values. In both high and low oxygen pressure interfaces, the electrical Hall mobilities follow a similar power-law dependence as observed in oxygen reduced STO bulk samples. The results are confirmed on a microscopic level by local strain fields at the interface reaching 10 nm into the STO substrate.
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