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- Brucas, Rimantas, 1965, et al.
(författare)
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Magnetic and transport properties of discontinuous Ni81 Fe19/Al2O3 multilayers
- 2007
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 310:2 SUPPL. PART 3, s. 2521-2523
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Tidskriftsartikel (refereegranskat)abstract
- The structural percolation and its correlation with the magnetic and transport properties of Ni 81 Fe 19 / Al 2 O 3 multilayer films were studied by varying the thickness (t) of the Ni 81 Fe 19 (permalloy, Py) layers in the range of 10-16 Å, while keeping the Al 2 O 3 layer thickness constant at 16 Å. Low-angle X-ray reflectivity and transmission electron microscopy measurements revealed a good structural quality of the multilayers and showed the transition from continuous Py layers (t = 16 over(A, ̊)) separated by Al 2 O 3 layers to grains (t = 10 over(A, ̊)) dispersed in the insulating matrix. Magnetization measurements showed the gradual transition from ferromagnetic layers (t = 16 over(A, ̊)) to superparamagnetic clusters (t = 12 over(A, ̊)) and isolated grains (t = 10 over(A, ̊)) that successively become blocked as the temperature decreases. The temperature dependence of the current in-plane (CIP) resistance of the samples reveals a change from typical metallic (d R / d T > 0) to dielectric (d R / d T
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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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| 5. |
- Hanson, Maj, 1939, et al.
(författare)
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Arrays of elliptical Fe(001) nanoparticles: Magnetization reversal, dipolar interactions, and effects of finite array sizes
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 2469-9950 .- 2469-9969 .- 1550-235X. ; 92:9
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of arrays of nanoparticles are determined by the interplay between the individual particle properties and the dipolar interactions between them. Here we present a study of arrays of elliptical Fe(001) particles of thickness 10–50 nm. The aspect ratios of the ellipses are 1:3, their short axes a=50, 100, or 150 nm, and the periodicity of the rectangular arrays is either two or four times the corresponding axes of the ellipses. Magnetic measurements together with numerical and micromagnetic calculations yield a consistent picture of the arrays, comprising single-domain nanoparticles. We show that the magnetization reversal, occurring in the range 100–400 mT for fields applied along the long axis, is mainly determined by the properties of the corresponding single Fe ellipses. The interaction fields of the order of tens of mT can be tuned by the array configurations. For the actual arrays the interactions promote switching. For film thicknesses below the Bloch wall width parameter of Fe, lw=22 nm, magnetization reversal occurs without formation of domain walls or vortices. Within this range arrays may be tuned to obtain a well-defined switching field. Two general conclusions are drawn from the calculations: the character of the interaction, whether it promotes or delays magnetization reversal, is determined by the aspect ratio of the array grid, and the interaction strength saturates as the size of the array increases.
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| 6. |
- Hanson, Maj, 1939, et al.
(författare)
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Domain walls in Fe(001) bicrystals – thickness dependence and field induced transitions
- 2007
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 310:2 SUPPL. PART 3, s. 2195 -2197
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic domain walls (DW's) formed at the grain boundary (GB) of epitaxial bicrystal Fe(0 0 1) films, thickness t = 50 and 70 nm, were studied by magnetic force microscopy. The "as-grown" samples displayed DW's with different magnetic contrast profiles yielding a single peak for t = 50 nm and a double peak with a change of sign at the centre of the wall for t = 70 nm. For t=50 nm the wall is characterised as an asymmetric Bloch wall. The double peak of the 70 nm thick film transformed into a single peak characteristic for a charged wall, when a field of 30 mT was applied along the GB. At remanence this domain wall relaxed to a regular Bloch wall divided into segments of alternating signs. © 2006 Elsevier B.V. All rights reserved.
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