论文题目反铁磁多重回线研究

论文题目反铁磁多重回线研究 摘要 最近十年时间，由于磁性材料以及铁电材料在高速存储及传感换能方面的应用，回线动力学和标度律理论开始受到人们的广泛重视。基于高频下畴反转动力学对于研究材料在不同频率下的响应和损耗特性是很有价值的。另外，作为一种典型的非平衡现象，动态回线蕴含了丰富的关于相变和临界问题的物理机制。在此基础上，标度律研究有助于从外表简单的回线当中挖掘出更深刻的有关畴反转和动力学相变的信息。 当周期振荡的外场加在一个互作用多体系统，例如铁磁体的时候，系统会有一个相应的滞后；这种滞后的响应就是磁滞回线。滞回现象在铁电铁磁等诸多我们称之为铁性的材料中出现。研究磁电滞回线在交变外场下的动力学性质的课题称为回线动力学。在此方面，二十年来，已经有不少实践和理论的工作发表。然而，研究者基本山都将目光专注于简单单回线的研究，对于非常重要的双回线动力学和标度行为却少有报道。双回线出现在反铁电(磁)体中及部分铁电体的临界点。双回线是多相竞争的结果，具有很多特殊性，本文将详述。 本文首先使用蒙特卡罗方法研究了反铁电的标度行为，得到了面积与频率及振幅的标度关系，在低频区，面积与频率呈严格的2/3次方指数律。 另一面，本文还独创地用两套序参量标示出反铁磁的自由能，定性地说明了用蒙特克罗方法画出的各式回线形状的产生机理。 最后，本文还成功使用蒙特卡罗方法成功地划出了多重回线，与朗道理论预言的一致。 In the recent ten years, dynamoics of hysteresishas attached many attentions for its important technological applications and intriguing physics. Stimulated by the recording or memory applications of magnetic and ferroelectric materials, a comprehensive understanding of kinetic of domain rehearsal is necessary. Furthermore, hysteresis, as a typical nonequilibrium response, leads to many novel physics effect. When a interacting many-body system, such as a magnet, is driven in time by external perturbation, such as a magnetic field the system can’t response instantaneously due to the relaxational delay. This delay in the dynamical response give rise to a non-vanishing area of magnetization-field loop, a phenomenon we term dynamic hysteresis. Hysteresis phenomenon is very common in many ferroelectric materials. Considerable efforts has been made to investingate dynamic hysteresis and scaling behavior both theoretically and experimentally in the past twenty years. However the dynamic and scaling behaveior of double hysteresis was rarely reported. Double hysterisis, found in antiferromagnetics and antiferroelectrics, has an equal significance as the single hysteresis. Our study focus on his subject. In this thesis, we assumes the Mont Carlo method to simulate the antielectric materials based on the ising model and achieves expected results of scaling behavior between the area of the double loop and the frequency of imposed fields. Also, we apply Landau theory to express the free energy of antieletrics by two sets of order parameter and thus plot a 2D chart which clearly delineates the distribution of energy gulf and crest of the system. By the virtue of this chart, many different kind of double hysteresis I get by Monte Carlo stimulation could be interpreted qualitatively. Finally，we also get multi-loop hysteresis by Monte Carlo method which matches the expectation of landau theory. 目录 第一章 前言 一.知识背景 1.铁电反铁电概念及其动态性质 2.铁电反铁电回线产生机理 3.研究回线的理论方法： 二.工作背景 三.反铁电回线的研究 1.蒙特卡罗方法研究反铁磁的标度行为 2.MC方法结合朗道理论对反铁磁回线形状的研究 3.多重回线 四．参考文献