A systematic study of the (Pr,Nd)-(Fe,Co)-B hard magnetic system offers the tantalizing opportunity to develop high-performance magnets that can operate in an unprecedented temperature range (5-600 K). The substitution of Nd with Pr can expand the application of RE2TM14B-type magnets to cryogenic applications like satellites, ion traps in quantum computers, and H2-liquifacation. Meanwhile, the partial replacement of Fe with Co [1] will extend the upper-temperature limit beyond what is now achieved by the partial substitution of Nd with much more critical heavy rare earths (Dy, Tb). What is more, the applicability of additive manufacturing to RE2TM14B-type magnets is greatly facilitated when Pr replaces Nd, offering enormous potential for innovative net-shape processing with minimum material waste [2]. From a fundamental point of view, the physics, thermodynamics and metallurgy at play need to be fully explored to realize the complete potential of this material system and may offer guidelines for the future development of other RE-TM phases.

In this talk, we will show how the processing–microstructure–physical property relationship for (Pr,Nd)-(Fe,Co)-B hard magnetic system has to be understood on a fundamental level to be able to design and fabricate permanent magnets by both hot-deformation and selective laser melting techniques. We will discuss the role of antiferromagnetic grain boundary phase (Nd,Pr)6Fe13Cu in the formation of a high coercivity state in these magnets [3]. Also, we will report our recent results obtained on (Pr,Nd)2(Fe,Co)14B single crystals (spontaneous magnetization, exchange stiffness, anisotropy constants) and by integrating this knowledge with extrinsic properties, we will discuss how to elucidate the origins of the high coercivity in these magnets in a large temperature range (~ 5 to 600 K).

This work was financially supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Project ID No. 405553726, TRR 270 and the RTG 2761 LokoAssist (Grant no. 450821862).

1. Y. Wu, K. P. Skokov, L. Schäfer, F. Maccari, H. Xu, X. Wang, C. Jiang and O. Gutfleisch. A systematic investigation of Pr-rich Pr-(Fe,Co)-B material system: Phase formation, microstructure and magnetic property. Acta Mater. 263, 119517 (2024)

2. L. Schäfer, K. Skokov, J. Liu, F. Maccari, T. Braun, S. Riegg, I. Radulov, J. Gassmann, H. Merschroth, J. Harbig, M. Weigold and O. Gutfleisch. Design and Qualification of Pr–Fe–Cu–B Alloys for the Additive Manufacturing of Permanent Magnets. Adv. Funct. Mater. 31, 2102148 (2021)

3. J. Liu, R. Xie, A. Aubert, L. Schäfer, H. Zhang, O. Gutfleisch and K. Skokov. Magnetic properties of Nd6Fe13Cu single crystals. Appl. Phys. Lett. 122, (2023)