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Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer

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ABSTRACT

A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe) and high magnetization (900–1,000 emu/cm3) characteristic of L10 phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.

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a Transmission electron microscopy (TEM) image of thin FePt layer on columnar CrV seed layer. b XRD pattern of the as-grown film stack. c Scanning electron microscopy (SEM) images of FePt patterns of 100 nm diameter (left) and 50 nm diameter (right), respectively. Insets show magnified views of the respective patterns for clarity.
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Figure 2: a Transmission electron microscopy (TEM) image of thin FePt layer on columnar CrV seed layer. b XRD pattern of the as-grown film stack. c Scanning electron microscopy (SEM) images of FePt patterns of 100 nm diameter (left) and 50 nm diameter (right), respectively. Insets show magnified views of the respective patterns for clarity.

Mentions: Figure 2a shows a TEM image of an as-grown FePt/CrV film stack. The CrV seed layer exhibits a well-developed columnar grain structure. From our previous study, the well-defined columnar grains of the CrV layer was found to induce perpendicularly oriented grains in a thin FePt overlayer, which resulted in L10 FePt film at a moderate temperature [20]. To confirm this, we performed a XRD measurement on the as-grown FePt/CrV film stack. As seen in Figure 2b, characteristic FCT (001) and (002) peaks are observed without any FCC peaks, indicating that the FePt film is really in the L10 phase. The noisy baseline and rather broad FePt peaks are probably due to the very small thickness (7 nm) of the FePt film. Using this L10 FePt film on a CrV seed layer, FePt patterned media were fabricated. Figure 2c shows the FePt patterns of different sizes (100 and 50 nm in diameter) fabricated by the combined use of E-beam lithography and Ar plasma etching. The FePt nano-columns having a circular cross section are regularly arrayed on the CrV/glass substrates. The spacing between neighboring nano-columns is the same as its diameter, making the pitch a twofold of the diameter (200 and 100 nm for the respective pattern). From the figure, it is apparent that FePt patterns down to 50 nm in size (100 nm in pitch) can be fabricated by our top-down approach. As a matter of fact, we confirmed that the pattern size could be reduced to 25 nm with 50 nm pitch. Below this size limit (25 nm), the nano-columns started to be deformed, leading to a partly connected array.


Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer
a Transmission electron microscopy (TEM) image of thin FePt layer on columnar CrV seed layer. b XRD pattern of the as-grown film stack. c Scanning electron microscopy (SEM) images of FePt patterns of 100 nm diameter (left) and 50 nm diameter (right), respectively. Insets show magnified views of the respective patterns for clarity.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3211176&req=5

Figure 2: a Transmission electron microscopy (TEM) image of thin FePt layer on columnar CrV seed layer. b XRD pattern of the as-grown film stack. c Scanning electron microscopy (SEM) images of FePt patterns of 100 nm diameter (left) and 50 nm diameter (right), respectively. Insets show magnified views of the respective patterns for clarity.
Mentions: Figure 2a shows a TEM image of an as-grown FePt/CrV film stack. The CrV seed layer exhibits a well-developed columnar grain structure. From our previous study, the well-defined columnar grains of the CrV layer was found to induce perpendicularly oriented grains in a thin FePt overlayer, which resulted in L10 FePt film at a moderate temperature [20]. To confirm this, we performed a XRD measurement on the as-grown FePt/CrV film stack. As seen in Figure 2b, characteristic FCT (001) and (002) peaks are observed without any FCC peaks, indicating that the FePt film is really in the L10 phase. The noisy baseline and rather broad FePt peaks are probably due to the very small thickness (7 nm) of the FePt film. Using this L10 FePt film on a CrV seed layer, FePt patterned media were fabricated. Figure 2c shows the FePt patterns of different sizes (100 and 50 nm in diameter) fabricated by the combined use of E-beam lithography and Ar plasma etching. The FePt nano-columns having a circular cross section are regularly arrayed on the CrV/glass substrates. The spacing between neighboring nano-columns is the same as its diameter, making the pitch a twofold of the diameter (200 and 100 nm for the respective pattern). From the figure, it is apparent that FePt patterns down to 50 nm in size (100 nm in pitch) can be fabricated by our top-down approach. As a matter of fact, we confirmed that the pattern size could be reduced to 25 nm with 50 nm pitch. Below this size limit (25 nm), the nano-columns started to be deformed, leading to a partly connected array.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe) and high magnetization (900–1,000 emu/cm3) characteristic of L10 phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.

No MeSH data available.


Related in: MedlinePlus