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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.

No MeSH data available.


a SEM image and b XRD pattern of FePt patterns of 100 nm diameter fabricated by the deposition-last process. The inset in a shows a magnified view of the pattern for clarity. c Comparison of M vs. H curves for the patterned medium in out-of-plane and in-plane directions.
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Figure 4: a SEM image and b XRD pattern of FePt patterns of 100 nm diameter fabricated by the deposition-last process. The inset in a shows a magnified view of the pattern for clarity. c Comparison of M vs. H curves for the patterned medium in out-of-plane and in-plane directions.

Mentions: To avoid this direct exposure of FePt film to Ar plasma, we modified the fabrication procedure of patterned media as illustrated in Figure 1b. Based on this deposition-last process, the FePt film remains intact because no ion impingement is involved in whole fabrication steps. Figure 4a shows the FePt patterns produced by a combination of E-beam lithography and FePt lift-off. The FePt patterns of 100 nm size (200 nm pitch) are circular in shape and uniformly spaced from their neighbors, making pattern quality comparable to that of the top-down patterns mentioned above (see Figure 2c for comparison). A XRD measurement on the deposition-last patterned medium confirms that this modified process allows for realization of the L10 phase in fine-patterned FePt, as seen from Figure 4b. Magnetic hysteresis loops for this deposition-last patterned medium are shown in Figure 4c for both applied field directions of out-of-plane and in-plane. Now, a perpendicular anisotropy is clearly observed, making the direction perpendicular to film plane a magnetic easy axis. The coercivities in out-of-plane and in-plane directions are approximately 3,000 and 600 Oe, respectively, resulting in Hc,out/Hc,in ≈ 5 for this patterned medium. The strong perpendicular magnetic anisotropy is also supported by the perfect squareness (Mr,out/Ms,out ≈ 1) of M-H curve in the out-of-plane direction, while this ratio falls to a half (Mr,in/Ms,in = 0.52) in film plane.


Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer
a SEM image and b XRD pattern of FePt patterns of 100 nm diameter fabricated by the deposition-last process. The inset in a shows a magnified view of the pattern for clarity. c Comparison of M vs. H curves for the patterned medium in out-of-plane and in-plane directions.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 4: a SEM image and b XRD pattern of FePt patterns of 100 nm diameter fabricated by the deposition-last process. The inset in a shows a magnified view of the pattern for clarity. c Comparison of M vs. H curves for the patterned medium in out-of-plane and in-plane directions.
Mentions: To avoid this direct exposure of FePt film to Ar plasma, we modified the fabrication procedure of patterned media as illustrated in Figure 1b. Based on this deposition-last process, the FePt film remains intact because no ion impingement is involved in whole fabrication steps. Figure 4a shows the FePt patterns produced by a combination of E-beam lithography and FePt lift-off. The FePt patterns of 100 nm size (200 nm pitch) are circular in shape and uniformly spaced from their neighbors, making pattern quality comparable to that of the top-down patterns mentioned above (see Figure 2c for comparison). A XRD measurement on the deposition-last patterned medium confirms that this modified process allows for realization of the L10 phase in fine-patterned FePt, as seen from Figure 4b. Magnetic hysteresis loops for this deposition-last patterned medium are shown in Figure 4c for both applied field directions of out-of-plane and in-plane. Now, a perpendicular anisotropy is clearly observed, making the direction perpendicular to film plane a magnetic easy axis. The coercivities in out-of-plane and in-plane directions are approximately 3,000 and 600 Oe, respectively, resulting in Hc,out/Hc,in ≈ 5 for this patterned medium. The strong perpendicular magnetic anisotropy is also supported by the perfect squareness (Mr,out/Ms,out ≈ 1) of M-H curve in the out-of-plane direction, while this ratio falls to a half (Mr,in/Ms,in = 0.52) in film plane.

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.