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Adaptive design of an X-ray magnetic circular dichroism spectroscopy experiment with Gaussian process modelling 被引量:4
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作者 Tetsuro Ueno Hideitsu Hino +3 位作者 Ai Hashimoto Yasuo Takeichi Masahiro Sawada Kanta Ono 《npj Computational Materials》 SCIE EI 2018年第1期639-646,共8页
Spectroscopy is a widely used experimental technique,and enhancing its efficiency can have a strong impact on materials research.We propose an adaptive design for spectroscopy experiments that uses a machine learning ... Spectroscopy is a widely used experimental technique,and enhancing its efficiency can have a strong impact on materials research.We propose an adaptive design for spectroscopy experiments that uses a machine learning technique to improve efficiency.We examined X-ray magnetic circular dichroism(XMCD)spectroscopy for the applicability of a machine learning technique to spectroscopy.An XMCD spectrum was predicted by Gaussian process modelling with learning of an experimental spectrum using a limited number of observed data points.Adaptive sampling of data points with maximum variance of the predicted spectrum successfully reduced the total data points for the evaluation of magnetic moments while providing the required accuracy.The present method reduces the time and cost for XMCD spectroscopy and has potential applicability to various spectroscopies. 展开更多
关键词 SPECTROSCOPY CIRCULAR SPECTROSCOPY
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Role of atomic-scale thermal fluctuations in the coercivity
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作者 Yuta Toga Seiji Miyashita +1 位作者 Akimasa Sakuma Takashi Miyake 《npj Computational Materials》 SCIE EI CSCD 2020年第1期1084-1090,共7页
The microscopic mechanism of coercivity at finite temperature is a crucial issue for permanent magnets.Here we present the temperature dependence of the coercivity of an atomistic spin model for the highest-performanc... The microscopic mechanism of coercivity at finite temperature is a crucial issue for permanent magnets.Here we present the temperature dependence of the coercivity of an atomistic spin model for the highest-performance magnet Nd_(2)Fe_(14)B.For quantitative analysis of the magnetization reversal with thermal fluctuations,we focus on the free energy landscape as a function of the magnetization.The free energy is calculated by the replica-exchange Wang–Landau method.This approach allows us to address a slow nucleation problem,i.e.,thermal activation effects,in the magnetization reversal.We concretely observed that the thermal fluctuations lead to a downward convexity in the coercivity concerning the temperature.Additionally,through analyzing the microscopic process of the thermal activation(nucleation),we discover the activation volume is insensitive to a magnetic field around the coercivity.The insensitivity explains the linear reduction of the free energy barrier by the magnetic field in the nucleation process. 展开更多
关键词 THERMAL ACTIVATION MAGNETIZATION
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