Presentation Information
[P2-44]High-performance Exchange-coupled Rare-earth Hard Magnetic Nano-composite Ribbons: Processing, Properties and Applications
*SHAMPA AICH1, Akila Raja2, Shrantik K Dey1, Gautam Sinha3 (1. Indian Institute of Technology (IIT) Kharagpur, WB-721302 (India), 2. Ames National Laboratory, IOWA, IA 50011 (United States of America), 3. Raja Ramanna Centre for Advanced Technology (RRCAT), Indore, MP-452013 (India))
Keywords:
Exchange,Rare-earth,Nanocomposite,Magnetic properties,Rapid solidification
The exchange-coupled rare-earth hard magnets have become more and more interesting and attractive due to their essential role in the space and transport industry to be used in some precious instruments, such as sensors, actuators, motors, and gyroscopes. Also, it’s been a big challenge to use rare-earth magnets in Electric Vehicles (EVs) and Hybrid Vehicles (HEVs), and in accelerator magnets (to be used in synchrotron radiation beam-line). Recently, some newly developed nanocomposites and thin-film magnets have been used as high-performance magnets in the MEMS or NEMS industry. Rare-earth permanent magnets have become the key materials for the development of a sustainable future because they are now used in many applications, contributing to energy saving and greenhouse gas reduction. The combination of Rare-earth (RE) and Transition metal (TM) is an ideal combination to make a high-performance magnet, as the RE provides the high magneto crystalline anisotropy (HA) and the TM provides the high magnetization (Ms) and high Curie temperature (TC).
In this work, the processing, crystal structures (phase formations), microstructures, magnetic properties, and temperature stability of nanocomposite Rare-earth (RE)–Transition-metal (TM) hard magnetic melt-spun ribbons are discussed in which nanocrystalline and sub-micro-crystalline dimensions of the hard- and soft-magnetic phases interact to promote intergrain ferromagnetic exchange coupling leading to consequent enhancement of remanent magnetization and the technologically important maximum energy density. The rapid solidification route (melt spinning) was used to develop Sm1-xRExCo5 and Nd2-xRExFe14B nanocomposite ribbons (RE=Dy and/or Gd) as they exhibited improved microstructure and better magnetic properties compared to the bulk materials due to the very high cooling rate achieved (109–1010 K/s) during the rapid solidification processing. The enhanced magnetic properties were observed when the rare-earth metals (Sm, Nd) were partially replaced with heavy lanthanides (Dy, Gd).
A combination of heavy rare-earths (Gd and Dy) in Sm0.6Gd0.4Dy0.1Co5 ribbon exhibited an optimum magnetic property; Hc=13.3 kOe (1.33 T), Mr=37.17 emu/g (330.35 kA/m), and (BH)max=16.6 MGOe at room temperature, with near zero α and β values). These results suggest that the Gd and Dy substituted SmCo-based ribbons can be used at higher temperature applications with Curie temperature (TC) of 869 K. In Nd2-xDyxFe14B ribbons, the highest coercivity and the highest remanence were observed as 26.86 kOe and 69.558 emu/g, respectively at room temperature with optimum α and β values which are quite comparable with the previously reported values in the literature. The addition of Dy improved the uniformity in the grain structure and reduced the grain size in the range of sub-micron to nano-dimension resulting in enhanced magnetic properties (remanence and exchange). The increased coercivity by Dy addition is attributed to the segregation of Dy at the interface between the matrix phase and the grain boundary phase which opposes the nucleation on the reverse domain during demagnetization. The reduced remanence (Mr/Ms) values of the melt-spun ribbons were observed as 0.7 and above with a maximum Mr/Ms of 0.8, which indicates a good exchange property of the ribbons.
References:
(1) R. Skomski and J. M. D. Coey, Magnetic anisotropy How much is enough for a permanent magnet, Scr. Mater., Vol. 112, 2016, pp. 3-8.
(2) K. J. Strnat, and R. M. W. Strnat, Rare earth-cobalt permanent magnets, J. Magn. Magn. Mater., Vol. 100, 1991, pp. 38-56.
(3) H. Akai, Maximum performance of permanent magnet materials, Scr. Mater., Vol. 154, 2018, pp. 300-304.
(4) K. Ren et al., NdFeB coercivity enhancement and temperature coefficient reduction by PrDyCo diffusion, J. Magn. Magn. Mater., Vol. 618, 2025, 172856, ISSN 0304-8853.
In this work, the processing, crystal structures (phase formations), microstructures, magnetic properties, and temperature stability of nanocomposite Rare-earth (RE)–Transition-metal (TM) hard magnetic melt-spun ribbons are discussed in which nanocrystalline and sub-micro-crystalline dimensions of the hard- and soft-magnetic phases interact to promote intergrain ferromagnetic exchange coupling leading to consequent enhancement of remanent magnetization and the technologically important maximum energy density. The rapid solidification route (melt spinning) was used to develop Sm1-xRExCo5 and Nd2-xRExFe14B nanocomposite ribbons (RE=Dy and/or Gd) as they exhibited improved microstructure and better magnetic properties compared to the bulk materials due to the very high cooling rate achieved (109–1010 K/s) during the rapid solidification processing. The enhanced magnetic properties were observed when the rare-earth metals (Sm, Nd) were partially replaced with heavy lanthanides (Dy, Gd).
A combination of heavy rare-earths (Gd and Dy) in Sm0.6Gd0.4Dy0.1Co5 ribbon exhibited an optimum magnetic property; Hc=13.3 kOe (1.33 T), Mr=37.17 emu/g (330.35 kA/m), and (BH)max=16.6 MGOe at room temperature, with near zero α and β values). These results suggest that the Gd and Dy substituted SmCo-based ribbons can be used at higher temperature applications with Curie temperature (TC) of 869 K. In Nd2-xDyxFe14B ribbons, the highest coercivity and the highest remanence were observed as 26.86 kOe and 69.558 emu/g, respectively at room temperature with optimum α and β values which are quite comparable with the previously reported values in the literature. The addition of Dy improved the uniformity in the grain structure and reduced the grain size in the range of sub-micron to nano-dimension resulting in enhanced magnetic properties (remanence and exchange). The increased coercivity by Dy addition is attributed to the segregation of Dy at the interface between the matrix phase and the grain boundary phase which opposes the nucleation on the reverse domain during demagnetization. The reduced remanence (Mr/Ms) values of the melt-spun ribbons were observed as 0.7 and above with a maximum Mr/Ms of 0.8, which indicates a good exchange property of the ribbons.
References:
(1) R. Skomski and J. M. D. Coey, Magnetic anisotropy How much is enough for a permanent magnet, Scr. Mater., Vol. 112, 2016, pp. 3-8.
(2) K. J. Strnat, and R. M. W. Strnat, Rare earth-cobalt permanent magnets, J. Magn. Magn. Mater., Vol. 100, 1991, pp. 38-56.
(3) H. Akai, Maximum performance of permanent magnet materials, Scr. Mater., Vol. 154, 2018, pp. 300-304.
(4) K. Ren et al., NdFeB coercivity enhancement and temperature coefficient reduction by PrDyCo diffusion, J. Magn. Magn. Mater., Vol. 618, 2025, 172856, ISSN 0304-8853.
