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Magnetic Nanoparticle Arrays Self-Assembled on Perpendicular Magnetic Recording Media.

Mohtasebzadeh AR, Ye L, Crawford TM - Int J Mol Sci (2015)

Bottom Line: This increase suggests magnetic nanoparticle interactions evolve from nanoparticle-nanoparticle interactions to cluster-cluster interactions as opposed to feature-feature interactions.We suggest the aspect ratio increase occurs because the magnetic field gradients are strongest near the transitions between recorded regions in perpendicular media.If these gradients can be optimized for assembly, strong potential exists for using perpendicular recording templates to assemble complex heterogeneous materials.

View Article: PubMed Central - PubMed

Affiliation: Smart State Center for Experimental Nanoscale Physics, Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208, USA. ramoh87@gmail.com.

ABSTRACT
We study magnetic-field directed self-assembly of magnetic nanoparticles onto templates recorded on perpendicular magnetic recording media, and quantify feature width and height as a function of assembly time. Feature widths are determined from Scanning Electron Microscope (SEM) images, while heights are obtained with Atomic Force Microscopy (AFM). For short assembly times, widths were ~150 nm, while heights were ~14 nm, a single nanoparticle on average with a 10:1 aspect ratio. For long assembly times, widths approach 550 nm, while the average height grows to 3 nanoparticles, ~35 nm; a 16:1 aspect ratio. We perform magnetometry on these self-assembled structures and observe the slope of the magnetic moment vs. field curve increases with time. This increase suggests magnetic nanoparticle interactions evolve from nanoparticle-nanoparticle interactions to cluster-cluster interactions as opposed to feature-feature interactions. We suggest the aspect ratio increase occurs because the magnetic field gradients are strongest near the transitions between recorded regions in perpendicular media. If these gradients can be optimized for assembly, strong potential exists for using perpendicular recording templates to assemble complex heterogeneous materials.

No MeSH data available.


Scanning Electron Microscope (SEM) images of nanoparticle self-assembly onto perpendicular media recorded with 750 nm wide regions of alternating magnetization direction (up and down), for different coating times: (A) 5 min; (B) 15 min; (C) 30 min; and (D) 60 min. Note the significant change in width as a function of time as well as the assembly of material into the gaps with increasing coverage.
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ijms-16-19769-f001: Scanning Electron Microscope (SEM) images of nanoparticle self-assembly onto perpendicular media recorded with 750 nm wide regions of alternating magnetization direction (up and down), for different coating times: (A) 5 min; (B) 15 min; (C) 30 min; and (D) 60 min. Note the significant change in width as a function of time as well as the assembly of material into the gaps with increasing coverage.

Mentions: Figure 1 A–D shows Scanning Electron Microscope (SEM) images of coupons coated for 5, 15, 30 and 60 min respectively. For both 5 and 15 min there are gaps between particles within the patterns, while these gaps are less noticeable for 30 and 60 min coatings, suggesting that features fill in and then grow in width as time progresses. There are also more non-assembled particles between features for 15 min than for 5 min. Figure 1C shows that while the widths at 5 and 15 min coatings are similar, the width nearly doubles for 30 min, i.e., the growth accelerates between 5 and 30 min. This acceleration is shown in Figure 2, which shows average feature width vs. coating time. The average width is obtained from 15 different SEM images of features that are analyzed with imageJ software. The average width is similar for 5 and 15 min, ~150 nm wide (150 and 158 nm respectively). By 60 min the feature width increases to 460 nm and then to 525 nm after 120 min. Thus after a slow initial assembly process, the feature width grows rapidly from 15–60 min and slows again beyond.


Magnetic Nanoparticle Arrays Self-Assembled on Perpendicular Magnetic Recording Media.

Mohtasebzadeh AR, Ye L, Crawford TM - Int J Mol Sci (2015)

Scanning Electron Microscope (SEM) images of nanoparticle self-assembly onto perpendicular media recorded with 750 nm wide regions of alternating magnetization direction (up and down), for different coating times: (A) 5 min; (B) 15 min; (C) 30 min; and (D) 60 min. Note the significant change in width as a function of time as well as the assembly of material into the gaps with increasing coverage.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4581324&req=5

ijms-16-19769-f001: Scanning Electron Microscope (SEM) images of nanoparticle self-assembly onto perpendicular media recorded with 750 nm wide regions of alternating magnetization direction (up and down), for different coating times: (A) 5 min; (B) 15 min; (C) 30 min; and (D) 60 min. Note the significant change in width as a function of time as well as the assembly of material into the gaps with increasing coverage.
Mentions: Figure 1 A–D shows Scanning Electron Microscope (SEM) images of coupons coated for 5, 15, 30 and 60 min respectively. For both 5 and 15 min there are gaps between particles within the patterns, while these gaps are less noticeable for 30 and 60 min coatings, suggesting that features fill in and then grow in width as time progresses. There are also more non-assembled particles between features for 15 min than for 5 min. Figure 1C shows that while the widths at 5 and 15 min coatings are similar, the width nearly doubles for 30 min, i.e., the growth accelerates between 5 and 30 min. This acceleration is shown in Figure 2, which shows average feature width vs. coating time. The average width is obtained from 15 different SEM images of features that are analyzed with imageJ software. The average width is similar for 5 and 15 min, ~150 nm wide (150 and 158 nm respectively). By 60 min the feature width increases to 460 nm and then to 525 nm after 120 min. Thus after a slow initial assembly process, the feature width grows rapidly from 15–60 min and slows again beyond.

Bottom Line: This increase suggests magnetic nanoparticle interactions evolve from nanoparticle-nanoparticle interactions to cluster-cluster interactions as opposed to feature-feature interactions.We suggest the aspect ratio increase occurs because the magnetic field gradients are strongest near the transitions between recorded regions in perpendicular media.If these gradients can be optimized for assembly, strong potential exists for using perpendicular recording templates to assemble complex heterogeneous materials.

View Article: PubMed Central - PubMed

Affiliation: Smart State Center for Experimental Nanoscale Physics, Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208, USA. ramoh87@gmail.com.

ABSTRACT
We study magnetic-field directed self-assembly of magnetic nanoparticles onto templates recorded on perpendicular magnetic recording media, and quantify feature width and height as a function of assembly time. Feature widths are determined from Scanning Electron Microscope (SEM) images, while heights are obtained with Atomic Force Microscopy (AFM). For short assembly times, widths were ~150 nm, while heights were ~14 nm, a single nanoparticle on average with a 10:1 aspect ratio. For long assembly times, widths approach 550 nm, while the average height grows to 3 nanoparticles, ~35 nm; a 16:1 aspect ratio. We perform magnetometry on these self-assembled structures and observe the slope of the magnetic moment vs. field curve increases with time. This increase suggests magnetic nanoparticle interactions evolve from nanoparticle-nanoparticle interactions to cluster-cluster interactions as opposed to feature-feature interactions. We suggest the aspect ratio increase occurs because the magnetic field gradients are strongest near the transitions between recorded regions in perpendicular media. If these gradients can be optimized for assembly, strong potential exists for using perpendicular recording templates to assemble complex heterogeneous materials.

No MeSH data available.