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Magnetic nanostructuring and overcoming Brown's paradox to realize extraordinary high-temperature energy products.

Balasubramanian B, Mukherjee P, Skomski R, Manchanda P, Das B, Sellmyer DJ - Sci Rep (2014)

Bottom Line: Here we achieve this goal in exchange-coupled hard-soft composite films by effective nanostructuring of high-anisotropy HfCo7 nanoparticles with a high-magnetization Fe65Co35 phase.An analysis based on a model structure shows that the soft-phase addition improves the performance of the hard-magnetic material by mitigating Brown's paradox in magnetism, a substantial reduction of coercivity from the anisotropy field.The nanostructures exhibit a high room-temperature energy product of about 20.3 MGOe (161.5 kJ/m(3)), which is a record for a rare earth- or Pt-free magnetic material and retain values as high as 17.1 MGOe (136.1 kJ/m(3)) at 180°C.

View Article: PubMed Central - PubMed

Affiliation: Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy, University of Nebraska, Lincoln, NE-68588 (USA).

ABSTRACT
Nanoscience has been one of the outstanding driving forces in technology recently, arguably more so in magnetism than in any other branch of science and technology. Due to nanoscale bit size, a single computer hard disk is now able to store the text of 3,000,000 average-size books, and today's high-performance permanent magnets--found in hybrid cars, wind turbines, and disk drives--are nanostructured to a large degree. The nanostructures ideally are designed from Co- and Fe-rich building blocks without critical rare-earth elements, and often are required to exhibit high coercivity and magnetization at elevated temperatures of typically up to 180 °C for many important permanent-magnet applications. Here we achieve this goal in exchange-coupled hard-soft composite films by effective nanostructuring of high-anisotropy HfCo7 nanoparticles with a high-magnetization Fe65Co35 phase. An analysis based on a model structure shows that the soft-phase addition improves the performance of the hard-magnetic material by mitigating Brown's paradox in magnetism, a substantial reduction of coercivity from the anisotropy field. The nanostructures exhibit a high room-temperature energy product of about 20.3 MGOe (161.5 kJ/m(3)), which is a record for a rare earth- or Pt-free magnetic material and retain values as high as 17.1 MGOe (136.1 kJ/m(3)) at 180°C.

No MeSH data available.


Related in: MedlinePlus

Nanostructuring.HAADF image and the corresponding EDS color maps for aligned Hf-Co:Fe-Co nanocomposite thin films having Fe-Co contents of (a), f = 0.22 and (b), f = 0.07. The color distributions for Hf (blue), Co (red), Fe (green), combined Hf and Co, and combined Hf, Co, and Fe are shown.
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f2: Nanostructuring.HAADF image and the corresponding EDS color maps for aligned Hf-Co:Fe-Co nanocomposite thin films having Fe-Co contents of (a), f = 0.22 and (b), f = 0.07. The color distributions for Hf (blue), Co (red), Fe (green), combined Hf and Co, and combined Hf, Co, and Fe are shown.

Mentions: To form exchange-coupled Hf-Co:Fe-Co nanocomposite films, the aligned Hf-Co nanoparticles are co-deposited with Fe and Co atoms. Figure 2 shows the HAADF images with the Z-contrast and corresponding EDS color maps for Hf-Co:Fe-Co nanocomposite films having different volume fractions f of the magnetically soft Fe-Co phase, namely f = 0.22 (or 22 vol.%, Fig. 2a) and f = 0.07 (Fig. 2b). The EDS color maps, where Hf, Co, and Fe are blue, red, and green, respectively, indicate that the Fe-Co region is Fe-rich (green). The Co distribution is not visible in the matrix film due to the black background, but the individual and combined color mappings of Hf and Co shows a Co-rich region at the surface as compared to the core due to the soft Fe-Co addition (Fig. 2a). Also, x-ray diffraction analysis shows that the soft phase exhibits a body-centered cubic structure similar to that of bulk Fe65Co35 (Fig. S5 in Supplementary Information). For the samples shown in Fig. 2a and 2b, the deposition time was controlled to yield low coverage densities (thickness), to reveal the distribution of the soft phase during nanostructuring and to show that the nanoparticles are coated with and surrounded by the Fe-Co alloy.


Magnetic nanostructuring and overcoming Brown's paradox to realize extraordinary high-temperature energy products.

Balasubramanian B, Mukherjee P, Skomski R, Manchanda P, Das B, Sellmyer DJ - Sci Rep (2014)

Nanostructuring.HAADF image and the corresponding EDS color maps for aligned Hf-Co:Fe-Co nanocomposite thin films having Fe-Co contents of (a), f = 0.22 and (b), f = 0.07. The color distributions for Hf (blue), Co (red), Fe (green), combined Hf and Co, and combined Hf, Co, and Fe are shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4151151&req=5

f2: Nanostructuring.HAADF image and the corresponding EDS color maps for aligned Hf-Co:Fe-Co nanocomposite thin films having Fe-Co contents of (a), f = 0.22 and (b), f = 0.07. The color distributions for Hf (blue), Co (red), Fe (green), combined Hf and Co, and combined Hf, Co, and Fe are shown.
Mentions: To form exchange-coupled Hf-Co:Fe-Co nanocomposite films, the aligned Hf-Co nanoparticles are co-deposited with Fe and Co atoms. Figure 2 shows the HAADF images with the Z-contrast and corresponding EDS color maps for Hf-Co:Fe-Co nanocomposite films having different volume fractions f of the magnetically soft Fe-Co phase, namely f = 0.22 (or 22 vol.%, Fig. 2a) and f = 0.07 (Fig. 2b). The EDS color maps, where Hf, Co, and Fe are blue, red, and green, respectively, indicate that the Fe-Co region is Fe-rich (green). The Co distribution is not visible in the matrix film due to the black background, but the individual and combined color mappings of Hf and Co shows a Co-rich region at the surface as compared to the core due to the soft Fe-Co addition (Fig. 2a). Also, x-ray diffraction analysis shows that the soft phase exhibits a body-centered cubic structure similar to that of bulk Fe65Co35 (Fig. S5 in Supplementary Information). For the samples shown in Fig. 2a and 2b, the deposition time was controlled to yield low coverage densities (thickness), to reveal the distribution of the soft phase during nanostructuring and to show that the nanoparticles are coated with and surrounded by the Fe-Co alloy.

Bottom Line: Here we achieve this goal in exchange-coupled hard-soft composite films by effective nanostructuring of high-anisotropy HfCo7 nanoparticles with a high-magnetization Fe65Co35 phase.An analysis based on a model structure shows that the soft-phase addition improves the performance of the hard-magnetic material by mitigating Brown's paradox in magnetism, a substantial reduction of coercivity from the anisotropy field.The nanostructures exhibit a high room-temperature energy product of about 20.3 MGOe (161.5 kJ/m(3)), which is a record for a rare earth- or Pt-free magnetic material and retain values as high as 17.1 MGOe (136.1 kJ/m(3)) at 180°C.

View Article: PubMed Central - PubMed

Affiliation: Nebraska Center for Materials and Nanoscience and Department of Physics and Astronomy, University of Nebraska, Lincoln, NE-68588 (USA).

ABSTRACT
Nanoscience has been one of the outstanding driving forces in technology recently, arguably more so in magnetism than in any other branch of science and technology. Due to nanoscale bit size, a single computer hard disk is now able to store the text of 3,000,000 average-size books, and today's high-performance permanent magnets--found in hybrid cars, wind turbines, and disk drives--are nanostructured to a large degree. The nanostructures ideally are designed from Co- and Fe-rich building blocks without critical rare-earth elements, and often are required to exhibit high coercivity and magnetization at elevated temperatures of typically up to 180 °C for many important permanent-magnet applications. Here we achieve this goal in exchange-coupled hard-soft composite films by effective nanostructuring of high-anisotropy HfCo7 nanoparticles with a high-magnetization Fe65Co35 phase. An analysis based on a model structure shows that the soft-phase addition improves the performance of the hard-magnetic material by mitigating Brown's paradox in magnetism, a substantial reduction of coercivity from the anisotropy field. The nanostructures exhibit a high room-temperature energy product of about 20.3 MGOe (161.5 kJ/m(3)), which is a record for a rare earth- or Pt-free magnetic material and retain values as high as 17.1 MGOe (136.1 kJ/m(3)) at 180°C.

No MeSH data available.


Related in: MedlinePlus