Role of atomic-scale thermal fluctuations in the coercivity  

作　　者：Yuta Toga Seiji Miyashita Akimasa Sakuma Takashi Miyake 

机构地区：[1]National Institute for Materials Science(NIMS),Tsukuba 305-0047,Japan [2]Elements Strategy Initiative Center for Magnetic Materials(ESICMM),Tsukuba,Japan [3]Institute for Solid State Physics,University of Tokyo,Kashiwa 277-8581,Japan [4]The Physical Society of Japan,Tokyo 113-0033,Japan [5]Department of Applied Physics,Tohoku University,Sendai 980-8579,Japan [6]National Institute of Advanced Industrial Science and Technology(AIST),Tsukuba 305-8568,Japan

出　　处：《npj Computational Materials》2020年第1期1084-1090,共7页计算材料学（英文）

摘　　要：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.

关 键 词：THERMAL ACTIVATION MAGNETIZATION 

分 类 号：TB30[一般工业技术—材料科学与工程]