| 1. |
- Felton, S., et al.
(författare)
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Micromagnetic studies of Fe/Co ellipses with competing anisotropy contributions
- 2004
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 272-276:SUPPL. 1, s. e1297-
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Tidskriftsartikel (refereegranskat)abstract
- The effects of competing magneto-crystalline and shape anisotropies on magnetization reversal were studied in situ in arrays of sub-micron Fe/Co ellipses of compositions Fe2/Co6 and Fe8/Co3 with magnetic force microscopy (MFM). A simple model assigning magnetization values to the different types of domain structures observed in the MFM images was used to estimate the field dependence of the total magnetization of a sample. The agreement with macroscopic magnetization measurements is discussed.
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| 2. |
- Hanson, Maj, 1939, et al.
(författare)
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Influence of post-annealing on the properties of Fe50Pt50 film and submicron size particles
- 2004
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 272-276:SUPPL. 1, s. e1297-
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of a 48 nm thick Fe50Pt50 film and submicron size elements made of the film were investigated. The initial film was grown by DC magnetron sputtering and post-annealed during 30 min at 300°C. Arrays of circular dots with diameters d = 200, 300 and 550 nm and a reference sample (diameter 1.7mm) were made of the film by electron lithography and Ar ion milling. After structural analysis by X-ray diffraction (XRD) and characterization by magnetization measurements and magnetic force microscopy, all samples were further annealed during 30min at 600°C. The XRD scans show that this led to an improvement of the crystalline quality in all samples, to a degree depending on the size of the dots. Both the structural and magnetic measurements imply that after the second heat treatment all samples have the easy magnetocrystalline direction (c-axis) mainly in the plane of the film, while the initial structures were characterized by a random distribution of c-axes.
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| 3. |
- Hanson, Maj, 1939, et al.
(författare)
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Magnetic domain structures in submicron-size particles of epitaxial Fe (001) films: shape anisotropy and thickness dependence
- 2002
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 66, s. 144419-1
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Tidskriftsartikel (refereegranskat)abstract
- In this work the influence of shape anisotropy on the magnetic hysteresis and zero-field magnetic domain state of submicron-size particles of Fe was investigated. Arrays of particles having circular (diameter dc=550 or 200 nm), rectangular (900 nm by 300 nm), or elliptical (450 nm by 150 nm) shape were prepared by electron lithography and ion-beam milling of epitaxial Fe (001) films of thicknesses t=50, 30, 15, and 10 nm. The samples were characterized by magnetization measurements and magnetic-force microscopy (MFM). All films have cubic anisotropy, for t=50, 30, and 15 nm with the same anisotropy constant as bulk Fe: K1=(4.30.1)104 J m-3. For t=10 nm the effective anisotropy is increased, K1=5.7104 J m-3, due to surface effects. The effects of the interplay between the magnotocrystalline and shape anisotropies are observed as the lateral extension of the films is decreased. The circular particles with dc=550 nm have closed magnetic domain structures with a fourfold symmetry, compatible with the magnetocrystalline anisotropy, for all thicknesses. In the rectangular particles a gradual change is observed as the thickness decreases. For t=50 nm a diamond structure comprising three closed-domain substructures is formed in the demagnetized state. The rectangles with t=30 and 15 nm are multidomains with the number of closed substructures decreasing to 2 and 2 or 1, respectively. The thickness dependence of the domain structure and an accompanying change of character in the MFM contrast are explained by an increasing amount of Neel component in the domain walls with a width that increases with decreasing film thickness. The rectangles with t=10 nm are quasisingle domains, forming a flower state. The small circular particles (dc=200 nm) and the elliptical ones, both with t=10 nm, are considered to be stable single domains in zero field. Judging from the hysteresis curves, magnetization reversal does not occur by coherent rotation in any of the particles
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| 4. |
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| 5. |
- Kazakova, O., et al.
(författare)
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Influence of interfaces on the magnetic properties of submicron elements
- 2004
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 272-276:III, s. 1640-1641
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the influence of interfaces on the properties of patterned elliptical elements made of epitaxial (BCC) Fe2/Co6 multilayers and polycrystalline Fe25Co75 alloy films, both containing 75 at% Co. Magnetic force microscopy shows that the formation of stable single domains in zero field is more likely in ellipses made of the alloy than of the multilayers. Magnetization measurements demonstrate considerably different behaviour of elements made of homogeneous and layered films, which imply that the magnetization reversal occurs through the formation of quasi-single domain states in the Fe25/Co75 ellipses and mainly by gradual rotation and switching in the FeCo elements.
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| 6. |
- Kazakova, O., et al.
(författare)
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Submicron size particles of Fe/Co multilayers: Effects of tunable anisotropy
- 2002
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Ingår i: INTERMAG Europe 2002 - IEEE International Magnetics Conference. - 0780373650 ; , s. Article number 1000796-
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Konferensbidrag (refereegranskat)abstract
- Particle arrays prepared by electron beam lithography and ion beam milling of magnetic films can be designed to yield a wide range of magnetic properties. The shape and size of the particles as well as the distance between them may be varied independently of each other. Furthermore, by choosing multilayers as starting materials the intrinsic magnetic properties, e.g. the crystalline anisotropy may be tuned. In the present work we have extended our earlier studies of fcc Co and Fe submicron structures, with an investigation of arrays of elliptical particles (150 nm x 450 nm x 20 nm) prepared of Fe/Co multilayers. In these the crystalline anisotropy varies between those of Co and Fe. The zero-field state of the magnetic particles, the strength of the dipolar interactions, as well as the processes of magnetization reversal vary significantly with the composition of the starting film. An example is shown in the magnetic force microscopy (MFM) images of 20 nm thick particles of elliptical shape made of pure Co with 100% single domains (See figure la), Fe2ML/Co6ML with 75% single domains and pure Fe with no single domains. The images represent the zero-field state after demagnetization. We conclude that the critical size at which the particles will form a stable single domain state in zero field varies in a way that can be explained by the magnetocrystalline anisotropy decreasing when going from Co to Fe/Co to Fe.
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