磁性随机存储器中调控磁化反转势垒降低临界电流密度研究

项目名称： 磁性随机存储器中调控磁化反转势垒降低临界电流密度研究

项目编号： No.61474007

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 无线电电子学、电信技术

项目作者： 滕蛟

作者单位： 北京科技大学

项目金额： 81万元

中文摘要： 磁性随机存储器（MRAM）极有可能成为下一代信息存储技术的首选。利用自旋转移矩效应（STT）反转铁磁层（FM）磁化方向， 是MRAM实现高阻态、低阻态转变的主要方式。STT面临的核心问题是降低临界电流密度（Jc），同时必须综合考虑磁电阻率（MR）、热稳定性（Ku）等因素。本项目提出了一种新的电控磁矩反转（ECMS）方式：在交换劲度（Aex）很小的交换偏置（EB）多层膜体系中，利用STT效应先翻界面磁矩，在铁磁/反铁磁（FM/AFM）界面形成平行界面的畴壁（PDW）。再通过Aex调控不对称反磁化行为（AMRB）类型，利用EB推动界面PDW自发地向远离FM/AFM界面的方向移动，直到扫过整个FM层。这种ECMS方式中，STT只需作用于FM层界面磁矩，需要克服的势垒能量从整个FM层的各向异性能变成了PDW的畴壁能，势垒的大小比传统的方式要低一半左右，可以大幅度降低Jc。

中文关键词： 磁性随机存储器；电控磁化反转；临界电流密度；交换耦合；磁化反转势垒

英文摘要： Magnetic random access memory (MRAM) is the most important choice of information storage of the next generation. Using spin transfer torque effect (STT) reversal ferromagnetic layer (FM) magnetization direction, the MRAM can realize the transformation between a high impedance state and a low resistance state. So far, the core problem of the STT facing the community is how to further reduce the critical current density, considering the integrated optimization of the magnetoresistance, the magnetic anisotropy, and the thermal stability. In this application, we propose a new method of the Electric controlled magnetization switching(ECMS): in an exchange-biased FM/AFM multilayers with small exchange stiffness (Aex), firstly reverse the pinning direction as well as the magnetization direction of the interfacial FM spins by the STT effect, forming an interfacial planar domain wall (PDW), secondly tune the asymmetric magnetization reversal behaviors (AMRB) of the exchange bias (EB) system, pushing the PDW through the FM layer spontaneously by the interfacial pinning effect. For this method of the ECMS, the STT effect only needs to be applied on the interfacial spins in the FM layer. Thus, the energy barrier of the magnetization reversal turns from the anisotropic energy of the whole FM layer to the domain wall energy of the PDW. The energy barrier is nearly halved, which would greatly reduce the critical current density (Jc) of the STT.

英文关键词： Magnetic Random access Memory;Electrically controlled magnetization switching;Critical current density;Exchange Coupling;Magnetization reversal barrier