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

Authors

Balamurugan Balasubramanian, University of Nebraska-LincolnFollow
Pinaki Mukherjee, University of Nebraska-LincolnFollow
Ralph A. Skomski, University of Nebraska-LincolnFollow
Priyanka Manchanda, University of Nebraska-LincolnFollow
Bhaskar Das, University of Nebraska-LincolnFollow
David J. Sellmyer, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

2014

Citation

Scientific Reports 2014

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/m³), 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/m3) at 180°C.