基于修正蒙特卡洛方法的交换偏置锻炼效应微观弛豫过程研究

项目名称： 基于修正蒙特卡洛方法的交换偏置锻炼效应微观弛豫过程研究

项目编号： No.11204026

项目类型： 青年科学基金项目

立项/批准年度： 2013

项目学科： 物理学I

项目作者： 胡勇

作者单位： 东北大学

项目金额： 25万元

中文摘要： 本项目将重点研究交换偏置锻炼效应的微观弛豫过程，以层状和颗粒状铁磁/反铁磁复合纳米系统为研究对象，并采用修正的蒙特卡洛方法。该方法除了考虑热扰动的影响外，还将严格计算每个自旋的能量，继而完全考虑它们在反转过程中受到的能垒影响。我们将系统地研究有限温度下锻炼效应受不同的外在因素，如温度、冷却场等，以及内在因素，如系统尺寸、界面耦合大小、各向异性易轴方向等影响的变化趋势，并据此提出可行的从锻炼效应中恢复交换偏置的方法。更重要的是，凭借计算机模拟的优势，我们将记录锻炼效应与对应的恢复效应发生过程中的系统微观自旋构型及能量分布随磁化次数变化的即时演变过程，以建立宏观现象与微观弛豫过程的一一对应关系。通过对照宏观的交换偏置场、矫顽场、磁化强度的行为与对应的微观自旋构型及能量分布变化，最终我们将直观地呈现出全部的交换偏置锻炼效应的微观弛豫过程图像，以阐明锻炼效应的起源及为实验提供理论依据。

中文关键词： 复合纳米系统；交换偏置；锻炼效应；微观弛豫过程；蒙特卡洛方法

英文摘要： In this project, the research emphasis is placed on the microscopic relaxation process of exchange-bias training effect. We adopt ferromagnetic/antiferromagnetic composite nanosystems with layered and granular morphologies as the research objects and perform a modified Monte Carlo method, which not only considers the thermal fluctuations, but also calculates exactly the energy of each spin and thus considers completely the energy barriers during the spin-reversal processes. We will study systematically the dependencies of training effect on different extrinsic factors such as temperature and cooling field as well as different intrinsic factors such as system size, interfacial coupling, and anisotropy easy-axis orientation at finite temperatures. Accordingly, we present the feasible methods to recover the exchange bias from the training effect. More importantly, by virtue of the advantages in computer simulations, we will record the instant evolutions of the microscopic spin configurations and energy distributions with magnetizing times during the occurrence processes of training and corresponding recovery effects, in order to establish the one-to-one correspondence between the macroscopic phenomena and the microscopic relaxation processes. Finally, by comparing between the macroscopic behaviors of exchange bias

英文关键词： composite nanosystem；exchange bias；training effect；microscopic relaxation process；Monte Carlo method