FF-05 Minnealloy: An Ultra-High Saturation Magnetization Soft Ferromagnet
Creators: Sean Bishop
Philippe Weck
Tyra Douglas
CJ Pearce
Daniel Lowry
Landon Schnebly
Dominic Bosomtwi
William Echtenkamp
and JP Wang
Publisher: name: IEEE
Year: 2025

Industry, telecommunications, and electrical grid technology rely on magnetic components such as inductors and transformers. However, the cores for many of these components contain critical materials [1] that are susceptible to availability and supply chain risks. A rare-earth and critical material free alternative called Minnealloy, α”-Fe16NC, is being developed to replaced grain oriented electrical steel (GOES), non-oriented electrical steel (NOES), and amorphous metal (AM). Minnealloy’s small magnetic coercivity (197 A/m bulk phase, ~5 A/m engineered [2,3]), intermediate resistivity (≥ 30 x 10-8 Ωm) and gargantuan magnetic flux density (≥ 2.47T) result in low losses and more power transferred per cycle than any existing transformer core material for a given mass or volume [4,5,6,7]. It is predicted to operate at higher frequencies (> 100 MHz) and known to operate at higher power, with comparable hysteresis and lower eddy current losses, than GOES, NOES, and AM. Replacing a silicon steel transformer core with Minnealloy will result in up to a 33% volume and weight reduction; replacing a high-frequency ferrite transformer core with Minnealloy will result in an 80% volume reduction. However, achieving high phase purity in bulk samples to demonstrate the expected material performance remains a challenge. In this talk, and accompanying conference paper, we will discuss powder and ribbon fabrication routes, magnetic properties measurements, density functional theory modeling, and a path to higher phase purity for commercial application. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.References: [1] D. J. Bauer, R. T. Nguyen, and B.J. Smith, “Critical Materials Assessment,” U.S. Department of Energy, Washington D.C., Rep. DOE/EE-2756, July 2023. [2] H. Giselher, "Modern soft magnets: Amorphous and nanocrystalline materials," Acta Mater., vol. 61, pp. 718-734, Feb. 2013. [3] F.C. Li, T. Liu, J.Y. Zhang, S. Shuang, Q. Wang, A.D. Wang, J.G. Wang, and Y. Yang, "Amorphous–nanocrystalline alloys: fabrication, properties, and applications," Mater. Today Adv., vol. 4, Dec. 2019. [4] M. D. Mehedi, Y. Jiang, P. K. Suri, D. J. Flannigan, and J-P Wang, “Minnealloy: a new magnetic material with high saturation flux density and low magnetic anisotropy,” J. Phys. D: Appl. Phys., vol. 50, no. 37, Aug. 2017. [5] X. Zhang and J-P Wang, "High saturation magnetization and low magnetic anisotropy Fe-CN martensite thin film," Appl. Phys. Lett., vol. 114, iss. 15, Apr. 2019. [6] G. Guo, J. Liu, and JP Wang, "Carbon and microstructure effects on the magnetic properties of Fe–CN soft magnetic materials (Minnealloy)," TMS 2020 149th Annual Meeting & Exhibition Supplemental Proceedings, pp. 1841-1852, Feb. 2020. [7] Y. Sugita, H. Takahashi, M. Komuro, M. Igarashi, R. Imura, and T. Kambe "Magnetic and electrical properties of single phase, single crystal Fe16N2 films epitaxially grown by molecular beam epitaxy," J. Appl. Phys., vol. 79, pp. 5576-5581, Apr. 1996.
Industry, telecommunications, and electrical grid technology rely on magnetic components such as inductors and transformers. However, the cores for many of these components contain critical materials [1] that are susceptible to availability and supply chain risks. A rare-earth and critical material free alternative called Minnealloy, α”-Fe16NC, is being developed to replaced grain oriented electrical steel (GOES), non-oriented electrical steel (NOES), and amorphous metal (AM). Minnealloy’s small magnetic coercivity (197 A/m bulk phase, ~5 A/m engineered [2,3]), intermediate resistivity (≥ 30 x 10-8 Ωm) and gargantuan magnetic flux density (≥ 2.47T) result in low losses and more power transferred per cycle than any existing transformer core material for a given mass or volume [4,5,6,7]. It is predicted to operate at higher frequencies (> 100 MHz) and known to operate at higher power, with comparable hysteresis and lower eddy current losses, than GOES, NOES, and AM. Replacing a silicon steel transformer core with Minnealloy will result in up to a 33% volume and weight reduction; replacing a high-frequency ferrite transformer core with Minnealloy will result in an 80% volume reduction. However, achieving high phase purity in bulk samples to demonstrate the expected material performance remains a challenge. In this talk, and accompanying conference paper, we will discuss powder and ribbon fabrication routes, magnetic properties measurements, density functional theory modeling, and a path to higher phase purity for commercial application. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.References: [1] D. J. Bauer, R. T. Nguyen, and B.J. Smith, “Critical Materials Assessment,” U.S. Department of Energy, Washington D.C., Rep. DOE/EE-2756, July 2023. [2] H. Giselher, "Modern soft magnets: Amorphous and nanocrystalline materials," Acta Mater., vol. 61, pp. 718-734, Feb. 2013. [3] F.C. Li, T. Liu, J.Y. Zhang, S. Shuang, Q. Wang, A.D. Wang, J.G. Wang, and Y. Yang, "Amorphous–nanocrystalline alloys: fabrication, properties, and applications," Mater. Today Adv., vol. 4, Dec. 2019. [4] M. D. Mehedi, Y. Jiang, P. K. Suri, D. J. Flannigan, and J-P Wang, “Minnealloy: a new magnetic material with high saturation flux density and low magnetic anisotropy,” J. Phys. D: Appl. Phys., vol. 50, no. 37, Aug. 2017. [5] X. Zhang and J-P Wang, "High saturation magnetization and low magnetic anisotropy Fe-CN martensite thin film," Appl. Phys. Lett., vol. 114, iss. 15, Apr. 2019. [6] G. Guo, J. Liu, and JP Wang, "Carbon and microstructure effects on the magnetic properties of Fe–CN soft magnetic materials (Minnealloy)," TMS 2020 149th Annual Meeting & Exhibition Supplemental Proceedings, pp. 1841-1852, Feb. 2020. [7] Y. Sugita, H. Takahashi, M. Komuro, M. Igarashi, R. Imura, and T. Kambe "Magnetic and electrical properties of single phase, single crystal Fe16N2 films epitaxially grown by molecular beam epitaxy," J. Appl. Phys., vol. 79, pp. 5576-5581, Apr. 1996.