Presentation Information
[P1-19]Features of the magnetization reversal processes in sintered permanent magnets Nd-Fe-B and Sm-Co type
*Andrey Urzhumtsev1,2, Viktoria Maltseva1, Alexey Volegov1 (1. Ural Federal University (Russia), 2. POZ-Progress LLC (Russia))
Keywords:
permanent magnets,coercivity,magnetisation reversal processes,pinning,nucleation
In the modern technology industry, there are a large number of areas for the application of hard magnetic materials, the main volumes of consumption of which fall on the energy sector for electric motors and generators. The issue of magnetization reversal mechanisms in sintered permanent magnets (PM) of the Nd-Fe-B and Sm-Co type remains controversial. The main reason for this is the complex heterogeneous micro- and nano-structure formed during sintering, the properties of which are difficult to describe using structural analysis and numerical modeling.
The paper presents a number of approaches to measuring and assessing magnetic properties that allow us to determine the role of each of the magnetization reversal mechanisms in the formation of the coercivity of the most common commercial magnets of the N35, N48, N48SH and Sm(Co, Fe, Zr, Cu)Z grades.
Magnetic measurements of the initial magnetization and susceptibility curves were carried out on MPMS XL 7 in fields up to 7 T. Magnetic susceptibility was measured in alternating AC magnetic field with an amplitude h ~ = 3.7 Oe and a frequency f = 7 Hz. Partial hysteresis loops were measured using a PPMS DynaCool with a VSM setup attachment in a field of up to 9 T with a step of 1 kOe.
The study analyzes initial magnetization curves σ(H) and σr(H) from a thermally demagnetized state, magnetic susceptibility curves χ(H) and χr(H), angular dependences of coercivity Hc(Θ) within the framework of the Kondorsky and Stoner-Wohlfarth models, assesses the reversible and irreversible contribution to magnetization, and evaluates the role of intergranular magnetostatic interaction. The results of the presented magnetometric methods are combined into a general concept for assessing the role of pinning, nucleation and coherent rotation in magnetization reversal processes for sintered PM.
The considered methods of analysis show that the mechanism of magnetization reversal in permanent magnets based on the Nd2Fe14B phase is more complex than predicted by purely nucleation or pinning models [1]. A similar picture is observed in magnets of Sm(Co, Fe, Zr, Cu)Z type [2], but the effects of changes in magnetic susceptibility, reversible contribution to magnetization and the role of magnetostatic interaction are manifested approximately an order of magnitude weaker than in Nd-Fe-B magnets.
The study showed that the approach under consideration for assessing the mechanism of formation of a high-coercivity state is an effective tool that complements such methods as microstructural analysis and numerical modeling and allows predicting the prevailing role of the pinning or nucleation. For example, it has been shown that in the Nd-Fe-B PM N35 grade magnetization reversal almost entirely through domain wall movements, while N48SH behaves close-up to nucleation process. It was found that the magnetization reversal mechanisms in sintered rare-earth permanent magnets can indicate themselves in a very diverse manner and are largely determined by the history of the creation of a given magnet and differ from PM the same type, but different grades.
This work was financially supported by FEUZ-2024-0060.
References
1. Urzhumtsev, A. N., Maltseva, V. E., Yarkov, V. Y., Volegov, A. S. (2022). A modified Kondorsky model for describing the magnetization reversal processes in Nd–Fe–B permanent magnets. Physics of Metals and Metallography, 123(11), 1054-1060.
2. Urzhumtsev, A., Maltseva, V., Volegov, A. (2022). Magnetization reversal processes in sintered permanent magnets Sm(Co, Fe, Zr, Cu)z. Journal of Magnetism and Magnetic Materials, 551, 169143.
The paper presents a number of approaches to measuring and assessing magnetic properties that allow us to determine the role of each of the magnetization reversal mechanisms in the formation of the coercivity of the most common commercial magnets of the N35, N48, N48SH and Sm(Co, Fe, Zr, Cu)Z grades.
Magnetic measurements of the initial magnetization and susceptibility curves were carried out on MPMS XL 7 in fields up to 7 T. Magnetic susceptibility was measured in alternating AC magnetic field with an amplitude h ~ = 3.7 Oe and a frequency f = 7 Hz. Partial hysteresis loops were measured using a PPMS DynaCool with a VSM setup attachment in a field of up to 9 T with a step of 1 kOe.
The study analyzes initial magnetization curves σ(H) and σr(H) from a thermally demagnetized state, magnetic susceptibility curves χ(H) and χr(H), angular dependences of coercivity Hc(Θ) within the framework of the Kondorsky and Stoner-Wohlfarth models, assesses the reversible and irreversible contribution to magnetization, and evaluates the role of intergranular magnetostatic interaction. The results of the presented magnetometric methods are combined into a general concept for assessing the role of pinning, nucleation and coherent rotation in magnetization reversal processes for sintered PM.
The considered methods of analysis show that the mechanism of magnetization reversal in permanent magnets based on the Nd2Fe14B phase is more complex than predicted by purely nucleation or pinning models [1]. A similar picture is observed in magnets of Sm(Co, Fe, Zr, Cu)Z type [2], but the effects of changes in magnetic susceptibility, reversible contribution to magnetization and the role of magnetostatic interaction are manifested approximately an order of magnitude weaker than in Nd-Fe-B magnets.
The study showed that the approach under consideration for assessing the mechanism of formation of a high-coercivity state is an effective tool that complements such methods as microstructural analysis and numerical modeling and allows predicting the prevailing role of the pinning or nucleation. For example, it has been shown that in the Nd-Fe-B PM N35 grade magnetization reversal almost entirely through domain wall movements, while N48SH behaves close-up to nucleation process. It was found that the magnetization reversal mechanisms in sintered rare-earth permanent magnets can indicate themselves in a very diverse manner and are largely determined by the history of the creation of a given magnet and differ from PM the same type, but different grades.
This work was financially supported by FEUZ-2024-0060.
References
1. Urzhumtsev, A. N., Maltseva, V. E., Yarkov, V. Y., Volegov, A. S. (2022). A modified Kondorsky model for describing the magnetization reversal processes in Nd–Fe–B permanent magnets. Physics of Metals and Metallography, 123(11), 1054-1060.
2. Urzhumtsev, A., Maltseva, V., Volegov, A. (2022). Magnetization reversal processes in sintered permanent magnets Sm(Co, Fe, Zr, Cu)z. Journal of Magnetism and Magnetic Materials, 551, 169143.