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- Rodmar, M., et al.
(författare)
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Magnetoresistance of icosahedral Al-Pd-Re : From weak localization through breakdown to a high-resistivity regime
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:6, s. 3936-3950
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Tidskriftsartikel (refereegranskat)abstract
- The magnetoresistance (MR) of icosahedral Al-Pd-Re of nominal composition Al(70.5)Pd(21)Res(8.5), and With resistance ratios R [=rho(4 K)/rho(295 K)] from 2 to 120, has been measured in the range 0.1-40 K in magnetic fields up to 12 T. Three regions of the MR can be distinguished. For R up to 13 quantum interference effects (QIE) describe the observations well. MR in excess of 100% was observed at low temperatures in this region. For R increasing above 13, the approach of a possible metal-insulator transition (MIT) can be followed in the results. A new negative MR contribution emerges at the lowest temperature, 0.2 K, and increases in magnitude with R. From analyses within QIE the Coulomb interaction parameter above R approximate to 10 and the inelastic-scattering time decrease with R, and the results indicate that this may be the case also for the spin-orbit-scattering rate. For R greater than or equal to 50, weak localization has broken down. Samples prepared by two different methods were studied in this region of R. Although the temperature dependence of the electrical resistivity and the MR at temperatures above 4 K are similar for similar R values in both sets of samples, significant differences were observed;below 1 K. We discuss this MR in the light of current theories on both sides of an MIT and conclude that none of these theories can fully reproduce the observed features for samples in this range.
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- Landälv, Ludvig, 1982-, et al.
(författare)
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Phase composition and transformations in magnetron-sputtered (Al,V)2O3 coatings
- 2019
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 688
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Tidskriftsartikel (refereegranskat)abstract
- Coatings of (Al1-xVx)2O3, with x ranging from 0 to 1, were deposited by pulsed DC reactive sputter deposition on Si(100) at a temperature of 550 °C. XRD showed three different crystal structures depending on V-metal fraction in the coating: α-V2O3 rhombohedral structure for 100 at.% V, a defect spinel structure for the intermediate region, 63–42 at.% V. At lower V-content, 18 and 7 at.%, a gamma-alumina-like solid solution was observed, shifted to larger d-spacing compared to pure γ-Al2O3. The microstructure changes from large columnar faceted grains for α-V2O3 to smaller equiaxed grains when lowering the vanadium content towards pure γ-Al2O3. Annealing in air resulted in formation of V2O5 crystals on the surface of the coating after annealing to 500 °C for 42 at.% V and 700 °C for 18 at.% V metal fraction respectively. The highest thermal stability was shown for pure γ-Al2O3-coating, which transformed to α-Al2O3 after annealing to 1100 °C. Highest hardness was observed for the Al-rich oxides, ~24 GPa. The latter decreased with increasing V-content, larger than 7 at.% V metal fraction. The measured hardness after annealing in air decreased in conjunction with the onset of further oxidation of the coatings.
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