Presentation Information
[P1-52]Anisotropy field measurement in hard magnets: evaluating current methodologies
*Alex Aubert1, Konstantin Skokov1, Oliver Gutfleisch1 (1. Functional Materials, TU Darmstadt (Germany))
Keywords:
Anisotropy field,methodology
With the exponential rise of data-driven materials research strategies, datasets play a crucial role in developing models and predicting material properties. However, machine learning requires accurate datasets and well-defined descriptors to ensure reliable predictions [1]. In the field of energy applications, the demand for high-performance and sustainable permanent magnets is growing, and machine learning has the potential to accelerate the discovery of new compositions. One of the key criteria for achieving hard magnetic properties is the anisotropy field HA [2].
Traditionally, HA is determined by using single crystals of a defined shape. However, growing phase-pure single crystals is not always feasible for certain hard magnetic compounds due to phase stability challenges. Researchers therefore employ alternatives such as aligned polycrystalline powder, but the results are not always accurate. In this study, we compare and evaluate the most commonly used methodologies for estimating the anisotropy field using Ce2Fe14B as a case study. Specifically, we assess different methods—including hard-axis saturation, magnetization area, Sucksmith-Thompson (S-T), the law of approach to saturation (LAS), and singular point detection (SPD)—applied to single crystals, aligned polycrystals powder, and isotropic bulk polycrystals.
Our results show that for single crystals, most of the methods provide accurate results within a 2% relative error when the demagnetizing field is properly accounted for. However, without demagnetizing field correction, an error of 9.5% was obtained in our case. The highest errors in HA are observed for aligned polycrystalline powders, reaching up to 17% compared to single-crystal data. Notably, the SPD method based on the first derivative of the magnetization curve, widely used in recent literature, did not provide accurate results for single crystals or aligned polycrystals. The underlying reasons are discussed in detail. In contrast, the SPD method utilizing a pulse magnetometer with second derivative analysis provides a reliable estimation of the anisotropy field for both single crystals and polycrystals (see Figure).These findings are particularly relevant for materials scientists seeking to use reliable descriptors in machine learning datasets and to accurately estimate the anisotropy field in new hard magnetic compounds.
References:
[1] R. Ramprasad et al. npj Comput Mater 3, 54 (2017)
[2] R. Skomski, and J. M. D. Coey. Scripta Materialia 112 (2016): 3-8.
Acknowledgement:
This work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Project ID no. 405553726-TRR 270.
Traditionally, HA is determined by using single crystals of a defined shape. However, growing phase-pure single crystals is not always feasible for certain hard magnetic compounds due to phase stability challenges. Researchers therefore employ alternatives such as aligned polycrystalline powder, but the results are not always accurate. In this study, we compare and evaluate the most commonly used methodologies for estimating the anisotropy field using Ce2Fe14B as a case study. Specifically, we assess different methods—including hard-axis saturation, magnetization area, Sucksmith-Thompson (S-T), the law of approach to saturation (LAS), and singular point detection (SPD)—applied to single crystals, aligned polycrystals powder, and isotropic bulk polycrystals.
Our results show that for single crystals, most of the methods provide accurate results within a 2% relative error when the demagnetizing field is properly accounted for. However, without demagnetizing field correction, an error of 9.5% was obtained in our case. The highest errors in HA are observed for aligned polycrystalline powders, reaching up to 17% compared to single-crystal data. Notably, the SPD method based on the first derivative of the magnetization curve, widely used in recent literature, did not provide accurate results for single crystals or aligned polycrystals. The underlying reasons are discussed in detail. In contrast, the SPD method utilizing a pulse magnetometer with second derivative analysis provides a reliable estimation of the anisotropy field for both single crystals and polycrystals (see Figure).These findings are particularly relevant for materials scientists seeking to use reliable descriptors in machine learning datasets and to accurately estimate the anisotropy field in new hard magnetic compounds.
References:
[1] R. Ramprasad et al. npj Comput Mater 3, 54 (2017)
[2] R. Skomski, and J. M. D. Coey. Scripta Materialia 112 (2016): 3-8.
Acknowledgement:
This work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Project ID no. 405553726-TRR 270.
