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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.


Atomic Force Microscopy (AFM) images of nanoparticle self-assembly onto the same features imaged with SEM in Figure 1, for different coating times: (A) 5 min; (B) 15 min; (C) 30 min; and (D) 60 min.
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ijms-16-19769-f003: Atomic Force Microscopy (AFM) images of nanoparticle self-assembly onto the same features imaged with SEM in Figure 1, for different coating times: (A) 5 min; (B) 15 min; (C) 30 min; and (D) 60 min.

Mentions: The SEM images in Figure 1 do suggest that the nanoparticle assemblies grow not only in width but also in height. To quantitatively measure feature height we employ Atomic Force Microscopy (AFM), as shown in Figure 3, where again A–D correspond to 5, 15, 30 and 60 min coatings times. For each coupon a cantilever with 300 kHz resonance frequency and 40 N/m force constant was used, and each coupon was scanned with 1024 pixel resolution in AC-Mode. Figure 3A shows an AFM image for a 5 min coating. In Figure 3 brighter features are higher. Similar to the SEM image in Figure 1A there are gaps within the patterns. Also, particles and crystals between arrays are noticeable in AFM imaging. We used Gwyddion software to subtract the background and analyze image line profiles from the AFM images.


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

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

Atomic Force Microscopy (AFM) images of nanoparticle self-assembly onto the same features imaged with SEM in Figure 1, for different coating times: (A) 5 min; (B) 15 min; (C) 30 min; and (D) 60 min.
© Copyright Policy
Related In: Results  -  Collection

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

ijms-16-19769-f003: Atomic Force Microscopy (AFM) images of nanoparticle self-assembly onto the same features imaged with SEM in Figure 1, for different coating times: (A) 5 min; (B) 15 min; (C) 30 min; and (D) 60 min.
Mentions: The SEM images in Figure 1 do suggest that the nanoparticle assemblies grow not only in width but also in height. To quantitatively measure feature height we employ Atomic Force Microscopy (AFM), as shown in Figure 3, where again A–D correspond to 5, 15, 30 and 60 min coatings times. For each coupon a cantilever with 300 kHz resonance frequency and 40 N/m force constant was used, and each coupon was scanned with 1024 pixel resolution in AC-Mode. Figure 3A shows an AFM image for a 5 min coating. In Figure 3 brighter features are higher. Similar to the SEM image in Figure 1A there are gaps within the patterns. Also, particles and crystals between arrays are noticeable in AFM imaging. We used Gwyddion software to subtract the background and analyze image line profiles from the AFM images.

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.