Presentation Information
[P2-60]Influence of Cobalt on the Coercivity of Sm(Fe,Ti,V)12-based Magnets
*Toni Subagja1,2, Jiasheng Zhang1, Andres Martin-Cid1, Anton Bolyachkin1, Nikita Kulesh1, Xin Tang1, Hossein Sepehri-Amin1,2 (1. National Institute for Materials Science (Japan), 2. Graduate School of Science and Technology, University of Tsukuba (Japan))
Keywords:
ThMn12,Magnetic Properties,Grain Boundary,Composition optimization
Rare-earth lean SmFe12-based compounds with a ThMn12-type crystal structure are considered strong candidates for next-generation high-performance permanent magnets. This is because they exhibit superior intrinsic magnetic properties compared to Nd2Fe14B, especially at the elevated temperatures1. However, the main challenge toward industrial application of SmFe12-based magnets is how to transfer their intrinsic magnetic properties to the extrinsic ones, large coercivity (µ0Hc) and remanence (µ0Mr). To address this, composition optimization is crucial. For instance, reducing non-magnetic elements and adding cobalt can improve saturation magnetization (µ0Ms)2. Additionally, extrinsic properties rely not only on the composition of the material but are also strongly affected by its microstructure. Factors like grain size, grain boundaries, and the overall composition greatly affect the performance3.
In this study, we investigated Sm8Zr2Fe76.5-xCoxTi8V5Cu0.5 and Sm8Zr2Fe76.5-xCoxTi5V8Cu0.5 ribbons with x = 0, 5.5, 11, and 15 at.%, referring to them as Ti-rich and Ti-lean samples, respectively. The alloys were first prepared by induction melting to create initial ingots, then rapidly solidified into ribbons using the melt-spinning technique. The as spun ribbons were annealed at 973 K and 1173 K for 30 minutes. The magnetic properties of the samples were characterized using a superconducting quantum interference device with a vibrating sample magnetometer (SQUID-VSM). Microstructure investigations were conducted using X-ray diffraction analysis, electron microscopy, atom probe tomography.
Figure 1(a) shows coercivity as a function of Co content in the Sm8Zr2Fe76.5-xCoxTi8V5Cu0.5 and Sm8Zr2Fe76.5-xCoxTi5V8Cu0.5 ribbons optimally annealed at 1173 K for 30 minutes. Our results reveal a distinct difference in coercivity reduction behavior between Ti-lean and Ti-rich ribbons. Ti-lean ribbons exhibit a more significant decrease in coercivity than that of Ti-rich ribbons upon addition of Co. Figure 1(b-e) shows general microstructure of optimally annealed Sm8Zr2Fe61.5Co15Ti8V5Cu0.5 ribbon. It was found that the microstructural origin for the 0.62 T coercivity in this sample is isolation of SmFe12-based grains with a size of below 500 nm with (Sm,Cu)-rich intergranular phase with a composition of Sm19.9Zr2.6Fe41.87Co15.41Ti4.8V4.67Cu6.35. Unlike the previous reports, Sm-rich intergranular phase can be formed even in the Ti-rich compositions. In this talk, the coercivity dependence of Ti-rich and Ti-lean alloys upon different content of Co will be discussed based on intrinsic magnetic properties of the alloys as well as the microstructural features.
References
1. Hirayama, Y., Takahashi, Y. K., Hirosawa, S. & Hono, K. Scripta Materialia 138 (2017) 62–65
2. P. Tozman, H. Sepehri-Amin et al. Scripta Materialia 258 (2025) 116491
3. Zhang et al. Acta Materialia 238 (2022) 118228
In this study, we investigated Sm8Zr2Fe76.5-xCoxTi8V5Cu0.5 and Sm8Zr2Fe76.5-xCoxTi5V8Cu0.5 ribbons with x = 0, 5.5, 11, and 15 at.%, referring to them as Ti-rich and Ti-lean samples, respectively. The alloys were first prepared by induction melting to create initial ingots, then rapidly solidified into ribbons using the melt-spinning technique. The as spun ribbons were annealed at 973 K and 1173 K for 30 minutes. The magnetic properties of the samples were characterized using a superconducting quantum interference device with a vibrating sample magnetometer (SQUID-VSM). Microstructure investigations were conducted using X-ray diffraction analysis, electron microscopy, atom probe tomography.
Figure 1(a) shows coercivity as a function of Co content in the Sm8Zr2Fe76.5-xCoxTi8V5Cu0.5 and Sm8Zr2Fe76.5-xCoxTi5V8Cu0.5 ribbons optimally annealed at 1173 K for 30 minutes. Our results reveal a distinct difference in coercivity reduction behavior between Ti-lean and Ti-rich ribbons. Ti-lean ribbons exhibit a more significant decrease in coercivity than that of Ti-rich ribbons upon addition of Co. Figure 1(b-e) shows general microstructure of optimally annealed Sm8Zr2Fe61.5Co15Ti8V5Cu0.5 ribbon. It was found that the microstructural origin for the 0.62 T coercivity in this sample is isolation of SmFe12-based grains with a size of below 500 nm with (Sm,Cu)-rich intergranular phase with a composition of Sm19.9Zr2.6Fe41.87Co15.41Ti4.8V4.67Cu6.35. Unlike the previous reports, Sm-rich intergranular phase can be formed even in the Ti-rich compositions. In this talk, the coercivity dependence of Ti-rich and Ti-lean alloys upon different content of Co will be discussed based on intrinsic magnetic properties of the alloys as well as the microstructural features.
References
1. Hirayama, Y., Takahashi, Y. K., Hirosawa, S. & Hono, K. Scripta Materialia 138 (2017) 62–65
2. P. Tozman, H. Sepehri-Amin et al. Scripta Materialia 258 (2025) 116491
3. Zhang et al. Acta Materialia 238 (2022) 118228
