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- 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. |
- Flovik, Vegard, et al.
(författare)
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Tailoring the magnetodynamic properties of nanomagnets using magnetocrystalline and shape anisotropies
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 92:10
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Tidskriftsartikel (refereegranskat)abstract
- Magnetodynamical properties of nanomagnets are affected by the demagnetizing fields created by the same nanoelements. In addition, magnetocrystalline anisotropy produces an effective field that also contributes to the spin dynamics. We show how the dimensions of magnetic elements can be used to balance crystalline and shape anisotropies, and that this can be used to tailor the magnetodynamic properties. We study ferromagnetic ellipses patterned from a 10-nm-thick epitaxial Fe film with dimensions ranging from 50x150 to 150x450 nm. The study combines ferromagnetic resonance (FMR) spectroscopy with analytical calculations and micromagnetic simulations, and proves that the dynamical properties can be effectively controlled by changing the size of the nanomagnets. We also show how edge defects in the samples influence the magnetization dynamics. Dynamical edge modes localized along the sample edges are strongly influenced by edge defects, and this needs to be taken into account in understanding the full FMR spectrum.
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| 3. |
- 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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| 8. |
- Saxegaard, Magne, et al.
(författare)
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Field and current-induced magnetization reversal studied through spatially resolved point-contacts
- 2010
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 107:10, s. 103909-
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: We present results from scanning tunneling microscopy based point-contact measurements of the local resistance in octagon shaped, Co (20 nm )/ Cu (5 nm )/ Fe 19 Ni 81(2.5 nm ) spin-valve rings. Through this technique one can detect the magnetoresistance with spatial resolution, and link it to magnetic domain wall motion within the ring. Measurements with varying currents indicate current-induced effects leading to offsets in the magnetic fields required for magnetic switching. The offsets can be attributed to current-induced spin-transfer torque effects for the thin Fe 19 Ni 81 layer and to Oersted field effects for the thick Co layer.Full-text · Article · Jun 2010 · Journal of Applied Physics
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