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Single crystalline cylindrical nanowires - toward dense 3D arrays of magnetic vortices.

Ivanov YP, Chuvilin A, Vivas LG, Kosel J, Chubykalo-Fesenko O, Vázquez M - Sci Rep (2016)

Bottom Line: Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge.In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities.The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories.

View Article: PubMed Central - PubMed

Affiliation: King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia.

ABSTRACT
Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge. One solution may be to use arrays of densely packed cobalt nanowires that have been efficiently fabricated by electrodeposition. In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities. The stable vortex state is observed in arrays of monocrystalline cobalt nanowires with diameters as small as 45 nm and lengths longer than 200 nm with vanishing magnetic cross talk between closely packed neighboring wires in the array. Lorentz microscopy, electron holography and magnetic force microscopy, supported by micromagnetic simulations, show that the structure of the vortex state can be adjusted by varying the aspect ratio of the nanowires. The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories.

No MeSH data available.


Related in: MedlinePlus

LorTEM images in over- (a) and under-focused (b) conditions of an array of NWs 45 nm in diameter and 55-nm long at remanence. The arrows show the transverse direction and the clockwise (red) and anticlockwise (blue) rotation of NW magnetization. As (c) shows schematically, the magnetic vortex acts as a convex or a concave lens, depending on its chirality, which creates a focus above or below the sample. Looking at these planes, we could detect the presence of a vortex state and determine its chirality. On the hologram image (d) the high- and low-phase values are represented by two color sequences that correspond to the clockwise and anticlockwise rotation of NW magnetization and (e) shows the contour lines corresponding to the B⊥.
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f3: LorTEM images in over- (a) and under-focused (b) conditions of an array of NWs 45 nm in diameter and 55-nm long at remanence. The arrows show the transverse direction and the clockwise (red) and anticlockwise (blue) rotation of NW magnetization. As (c) shows schematically, the magnetic vortex acts as a convex or a concave lens, depending on its chirality, which creates a focus above or below the sample. Looking at these planes, we could detect the presence of a vortex state and determine its chirality. On the hologram image (d) the high- and low-phase values are represented by two color sequences that correspond to the clockwise and anticlockwise rotation of NW magnetization and (e) shows the contour lines corresponding to the B⊥.

Mentions: LorTEM images corresponding to the square region (marked in red in Fig. 2a) of the array of single-crystal hcp Co NWs are shown in Fig. 3a,b. We observed that most of the NWs with a circular cross section had a bright spot in the center either in over- or under-focused conditions, indicating the presence of vortices with different chirality. Some NWs had broader spots (Fresnel fringes due to differences in electrostatic potential in the Co and alumina), whose positions shifted slightly in over- and under-focused conditions. These shifts are indicative of the presence of a linear, in-plane magnetic-field component that is perpendicular to the shift vector. Thus, we concluded that some NWs were partly magnetized in plane of the section while others contained vortices of different chirality.


Single crystalline cylindrical nanowires - toward dense 3D arrays of magnetic vortices.

Ivanov YP, Chuvilin A, Vivas LG, Kosel J, Chubykalo-Fesenko O, Vázquez M - Sci Rep (2016)

LorTEM images in over- (a) and under-focused (b) conditions of an array of NWs 45 nm in diameter and 55-nm long at remanence. The arrows show the transverse direction and the clockwise (red) and anticlockwise (blue) rotation of NW magnetization. As (c) shows schematically, the magnetic vortex acts as a convex or a concave lens, depending on its chirality, which creates a focus above or below the sample. Looking at these planes, we could detect the presence of a vortex state and determine its chirality. On the hologram image (d) the high- and low-phase values are represented by two color sequences that correspond to the clockwise and anticlockwise rotation of NW magnetization and (e) shows the contour lines corresponding to the B⊥.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814901&req=5

f3: LorTEM images in over- (a) and under-focused (b) conditions of an array of NWs 45 nm in diameter and 55-nm long at remanence. The arrows show the transverse direction and the clockwise (red) and anticlockwise (blue) rotation of NW magnetization. As (c) shows schematically, the magnetic vortex acts as a convex or a concave lens, depending on its chirality, which creates a focus above or below the sample. Looking at these planes, we could detect the presence of a vortex state and determine its chirality. On the hologram image (d) the high- and low-phase values are represented by two color sequences that correspond to the clockwise and anticlockwise rotation of NW magnetization and (e) shows the contour lines corresponding to the B⊥.
Mentions: LorTEM images corresponding to the square region (marked in red in Fig. 2a) of the array of single-crystal hcp Co NWs are shown in Fig. 3a,b. We observed that most of the NWs with a circular cross section had a bright spot in the center either in over- or under-focused conditions, indicating the presence of vortices with different chirality. Some NWs had broader spots (Fresnel fringes due to differences in electrostatic potential in the Co and alumina), whose positions shifted slightly in over- and under-focused conditions. These shifts are indicative of the presence of a linear, in-plane magnetic-field component that is perpendicular to the shift vector. Thus, we concluded that some NWs were partly magnetized in plane of the section while others contained vortices of different chirality.

Bottom Line: Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge.In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities.The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories.

View Article: PubMed Central - PubMed

Affiliation: King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia.

ABSTRACT
Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge. One solution may be to use arrays of densely packed cobalt nanowires that have been efficiently fabricated by electrodeposition. In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities. The stable vortex state is observed in arrays of monocrystalline cobalt nanowires with diameters as small as 45 nm and lengths longer than 200 nm with vanishing magnetic cross talk between closely packed neighboring wires in the array. Lorentz microscopy, electron holography and magnetic force microscopy, supported by micromagnetic simulations, show that the structure of the vortex state can be adjusted by varying the aspect ratio of the nanowires. The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories.

No MeSH data available.


Related in: MedlinePlus