混自旋Ising钻石链的磁化特性及热力学性质研究

发布时间：2018-01-08 03:24

本文关键词：混自旋Ising钻石链的磁化特性及热力学性质研究　出处：《沈阳工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：由于一些有机高聚物和含铜的化合物在磁学研究中都可以抽象成一维钻石链模型,因此理论研究钻石链模型的磁化特性对于这类结构材料的实验及应用具有一定的指导意义。本文利用相关有效场理论,在晶场和横场共同作用的条件下,建立亚铁磁/铁磁混自旋Ising钻石链模型,推导出系统的磁矩和磁化率等计算公式。通过matlab软件编写程序,利用数值计算研究各种参数如交换作用、横场和晶场等对亚铁磁/铁磁混自旋Ising钻石链的磁矩、磁化率、截止温度、内能、比热和磁滞回线的影响。亚铁磁混自旋Ising钻石链的磁矩曲线出现阶梯效应,阶梯数随着交换作用及磁晶各向异性值的增大而减少;系统总的平均磁矩随温度的增加而减小,在同一温度下,随着横场的增大而减小,随着交换作用和晶场值的增加而减小,随着外磁场的增大而增大;磁化率随温度变化的曲线出现一个峰值,对应的温度叫做截止温度,当温度高于截止温度时,系统由亚铁磁性转变为超顺磁性;系统内能随温度的升高不断增加,在截止温度附近,内能随温度变化的趋势发生改变,内能曲线的斜率达到最大值,超过该最大值,内能随温度增加的趋势变得缓慢;比热曲线在一定参数范围内出现两个峰值,这是由于交换作用和横场较小或外磁场较大而引起的;系统矫顽力随交换作用|1J|的增大而增大,随A子格晶场|1D|、横场2Ω和温度TkB的增加而减小;磁滞回线随着横场1Ω、交换作用|1J|、C子格的晶场|2D|和温度TkB的变化出现零到七个环之间的变化,环的面积也随之发生改变。铁磁系统的混自旋Ising钻石链的磁矩曲线也会出现阶梯效应,阶梯数随交换作用的增加而减少,随晶场|1D|的增加先增多后减少,随晶场|2D|的增加变化比较剧烈。系统总的平均磁矩随温度的增加而减小,在同一温度下,随着交换作用和外磁场的增大而增大,随晶场值和横场的增大而减小;磁化率随温度变化的曲线也出现一个峰值,对应的温度即截止温度,当温度高于截止温度时,系统由铁磁性转变为超顺磁性;系统内能和比热随温度变化的规律与亚铁磁系统相类似,与其不同的是当外磁场较小时,比热曲线出现两个峰值;磁滞回线最多出现三个环,环数随交换作用1J和晶场|2D|的增加先增多后减少,随横场1Ω和温度TkB的增加而减少。研究结果表明,磁矩曲线会出现阶梯效应及多环的磁滞回线,这些特性在磁存储材料中有着潜在的、巨大的应用前景。
[Abstract]:Because of some organic polymer and copper containing compounds can be abstracted into a one-dimensional chain model in magnetism of diamond, so the magnetization characteristics of diamond chain theory research model has certain guiding significance for the experiment and application of this kind of structural material. By using effective field theory in the crystal field and transverse field interaction conditions establish, ferrimagnetic / ferromagnetic mixed spin Ising diamond chain model, derived the magnetic moment and the magnetic susceptibility formula. Through the MATLAB software program, various parameters are calculated by numerical studies such as exchange interaction, transverse field and crystal field of ferrimagnetic / ferromagnetic mixed spin Ising diamond chain magnetic moment, magnetic susceptibility stop temperature, internal energy, specific heat effect and hysteresis loop. The magnetic moment curve of ferrimagnetic mixed spin Ising diamond chain ladder effect, with the increase of the number of steps exchange effect and magnetic anisotropy value and To reduce the total system; the average magnetic moment decreases with the increase of temperature, at the same temperature, decreases with increasing transverse field, and decreases with the exchange and increase in value increases with the increase of the external magnetic field; magnetic susceptibility with temperature change curve appeared a peak corresponding to the temperature is called off the temperature, when the temperature is higher than the cut-off temperature, system transition from ferrimagnetic to superparamagnetic; system can increase with the increase of temperature, the cut-off temperature near the internal energy changes with the temperature change, the slope of the curve can reach the maximum value, exceeding the maximum value, can increase with the temperature trend becomes slow; specific heat curve showed two peaks in the range of parameters, this is due to the exchange interaction and the transverse field of magnetic field is smaller or larger; the system of coercive force increases with the exchange of |1J|, with the A sublattice Crystal field |1D|, transverse field and 2 temperature TkB decreases; the hysteresis loop with a transverse field of 1 ohm, |1J| exchange interaction, the crystal field |2D| and temperature change of TkB C sublattice is changed between zero to seven ring ring, the area was also changed. The ferromagnetic mixed spin system Ising diamond chain moment curve will also appear step effect, the number of steps decreases with the increasing of exchange interaction, with the increase of |1D| crystal field increased first and then decreased with the increase of |2D|, the crystal field changed dramatically. The average magnetic moment the total system decreases with the increase of temperature, at the same temperature, and increases with the increase of increase the exchange interaction and the external magnetic field, and the increase of transverse field decreases with crystal field; temperature dependent magnetic susceptibility curve also appeared a peak corresponding to the temperature cutoff temperature, when the temperature is higher than the cut-off temperature when the system changes from ferromagnetic to superparamagnetic; system of internal energy and specific heat With the temperature change rule and ferrimagnetic systems similar to, but it is different when the external magnetic field is small, the specific heat curve has two peaks; the hysteresis loop of a maximum of three ring ring, with the number of exchange increase the role of 1J and the crystal field of |2D| first increased and then decreased, and decreased with increasing transverse field and 1 temperature TkB the research results show that the magnetic hysteresis loop curve will show the step effect and polycyclic, these properties in magnetic storage materials have potential and great prospect.

【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB30

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