基于OPWP算法力磁耦合磁记忆信号特征研究

铁磁材料的塑性变形是严重影响其使用安全的隐患,对其有效检测可以预防破坏事故的发生。磁记忆检测技术可以实现对应力集中引起的材料塑性变形的检测。本文基于密度泛函理论建立铁磁晶体磁记忆检测模型,采用正交化平面波赝势法(OPWP)计算了体心立方晶体结构的铁在塑性变形后力磁耦合磁记忆检测信号的变化特征。结果表明:铁磁材料在塑性变形后晶格结构及能带分布发生改变,仍表现一定的铁磁性但磁性减弱。在受力过程中,晶体内部电子间交换关联作用过程改变,进而导致晶体能带向低能带底移动,轨道电子分布局域性增强,力磁耦合程度减弱。自旋向上和自旋向下的电子态密度分布改变,原子磁矩减小。宏观表现为:磁记忆信号强度下降,磁场变化率与未塑性变形铁相比减小,实验曲线斜率降低,材料整体磁特性减弱。

Study on force magnetic coupling magnetic memory signal characteristics based on OPWP algorithm

The plastic deformation of ferromagnetic material is a hidden trouble seriously affecting its safety in usage. Damage accident can be avoided if the plastic deformation is effectively tested. Magnetic memory test technology can test the material plastic deformation areas caused by stress concentration. In this paper, a magnetic memory test model of ferromagnetic crystal is built based on density functional theory. The orthogonalized plane wave pseudopotential (OPWP) algorithm is used to calculate the force magnetic coupling magnetic memory signal characteristics of bcc Fe crystal structure under plastic deformation. The results show that the lattice structure and band distribution change when the ferromagnetic material plastic deformation emerges. The ferromagnetism still exists but the magnetic characteristic weakens. When the stress is applied on the crystal, the course of exchange correlation among electrons inside the crystal is changed, which causes the crystal band structure moves towards the band bottom. The locality of orbital electron distribution is enhanced. The level of force magnetic coupling is weakened. In addition, the density distribution of the electron states of spin up and spin down is changed, and the atomic magnetic moment gradually decreases. The macro performance indication involves magnetic memory signal intensity drops, the magnetic field change rate decreases compared with that for no plastic deformation Fe, the slope of the experiment curve decreases, and the overall magnetic characteristic of the material weakens.