基于密度泛函理论的磁记忆信号产生机理研究

Mechanism study on magnetic memory signal based on density functional theory

与传统的无损检测技术相比,金属磁记忆方法对铁磁材料早期损伤的诊断更为有效。为了研究磁记忆自发漏磁信号的产生机理,采用基于密度泛函理论的第一性原理平面波赝势算法建立了磁力学模型,在此基础上,通过计算晶格结构、原子磁矩、系统能量与力的定量变化关系来研究力对材料磁性能的影响,进而分析力与磁记忆自发漏磁信号的关系。研究结果表明:外部载荷作用导致晶格畸变是磁记忆信号产生的根本原因,并且流水静压力导致的晶格畸变比正压力导致的晶格畸变对自发漏磁信号的影响要大;常温下理论计算得到的磁记忆信号随压力增加而线性变化的规律与实验结果具有很好的一致性。

Compared with traditional non-destructive testing methods, the technique of metal magnetic memory is a more effective way in evaluating early damages of ferromagnets due to the existence of material stresses. In this paper, a magneto-mechanical model is established with the plane wave and pseudo-potential method based on density func- tional theory （DFT） , and the quantitative relationships between load and magnetism performance are investigated through calculating lattice structure, atomic magnetic moment and system energy;and then, the influence laws of the pressure to spontaneous magnetic flux leakage （SMFL） signals are analyzed. The research results show that the lat- tice flow the mal distortion caused by external load results in the magnetic memory SMFL signals. The lattice distortion caused static pressure has more important influence to SMFL signals than that caused by positive pressure. In additic linear changing rule of magnetic memory signals versus pressure obtained from theoretical calculation under n temperature agrees with the experimental results very well.