Limits...
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

Magnetic properties.(a), Coercivity Hc and saturation magnetic polarization Js measured at 300 K as a function of Fe-Co content f. (b), A thin film model structure with a total area of 10 nm × 10 nm and having a soft-phase content f ≈ 0.25 (bottom) and a three-dimensional visualization of the onset of magnetization reversal or nucleation mode ϕ (top).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4151151&req=5

f4: Magnetic properties.(a), Coercivity Hc and saturation magnetic polarization Js measured at 300 K as a function of Fe-Co content f. (b), A thin film model structure with a total area of 10 nm × 10 nm and having a soft-phase content f ≈ 0.25 (bottom) and a three-dimensional visualization of the onset of magnetization reversal or nucleation mode ϕ (top).

Mentions: Figure 4a shows the measured room-temperature values of the coercivity Hc and of the saturation polarization Js = 4πMs as a function of f. As expected from the volume fractions of the two phases, Js continuously increases from 10.8 to 23.5 kG as the volume fraction f of the soft phase increases from 0 to 1. On the other hand, Hc initially increases from 8.65 kOe to 10.1 kOe on increasing the soft phase content from 0 to 0.07, and then continuously decreases on further addition of the soft phase. The initial increase of Hc reflects the formation of the composite nanostructure and is probably caused by reduced real-structure imperfections upon surface coating and/or a comparatively better easy-axis alignment32.


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)

Magnetic properties.(a), Coercivity Hc and saturation magnetic polarization Js measured at 300 K as a function of Fe-Co content f. (b), A thin film model structure with a total area of 10 nm × 10 nm and having a soft-phase content f ≈ 0.25 (bottom) and a three-dimensional visualization of the onset of magnetization reversal or nucleation mode ϕ (top).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Magnetic properties.(a), Coercivity Hc and saturation magnetic polarization Js measured at 300 K as a function of Fe-Co content f. (b), A thin film model structure with a total area of 10 nm × 10 nm and having a soft-phase content f ≈ 0.25 (bottom) and a three-dimensional visualization of the onset of magnetization reversal or nucleation mode ϕ (top).
Mentions: Figure 4a shows the measured room-temperature values of the coercivity Hc and of the saturation polarization Js = 4πMs as a function of f. As expected from the volume fractions of the two phases, Js continuously increases from 10.8 to 23.5 kG as the volume fraction f of the soft phase increases from 0 to 1. On the other hand, Hc initially increases from 8.65 kOe to 10.1 kOe on increasing the soft phase content from 0 to 0.07, and then continuously decreases on further addition of the soft phase. The initial increase of Hc reflects the formation of the composite nanostructure and is probably caused by reduced real-structure imperfections upon surface coating and/or a comparatively better easy-axis alignment32.

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