两层对称铁磁薄膜中的自旋波本征模

在非周期性边界条件和在考虑表面各向异性场的情况下 ,应用界面重参数化方法精确求解了两层对称铁磁薄膜中的低能自旋波本征问题 .结果表明 :表面各向异性场对各种模的表面性质影响很大     

各向异性对非对称薄膜中的自旋波的影响

采用界面重标度(IR)方法〔1〕,研究了非周期性边界条件下,双层非对称铁磁薄膜中自旋波的本征值问题,并计入体单轴各向异性,讨论了其对非对称铁磁薄膜中自旋波色散关系以及其波形的影响.结果表明:体单轴各向异性对非对称铁磁薄膜中的自旋波的影响很大,情况也较复杂.具体来说,随着两层薄膜中某一层的体各向异性常数的增加,体模和相应层内的禁闭模均有所变化(包括数目和数值),在整个变化过程中,光学-光学界面模的数目不变,本征模能量随DA(体各向异性)的增加而线性减小,而且,体单轴各向异性对各种自旋波本征模的波形影响也很大.     

双层对称薄膜中自旋波存在条件与各向异性

采用界面重标度(IR)方法，研究了非周期性边界条件下，双层铁磁薄膜中自旋波的本征值问题及对称薄膜中自旋波的存在条件；并计入体单轴各向异性，讨论了其对对称铁磁薄膜中自旋波色散关系及波形的影响，结果表明：在完全对称情况下，该系统除了可能存在一支光学——光学界面模外，只存在体模一种形式．而且，体单轴各向异性除了对本征模能量有影响外，对自旋波的色散曲线趋势及波形都没有影响．     

对称双层铁磁膜中的界面自旋波

运用改进的界面重参数方法,讨论了周期边界条件下对称双层铁磁膜中自旋波本征激发问题,系统中可以存在两种本征模:体模和界面模,并给出系统的色散关系和布里渊能带的精细结构.在此基础上重点分析了界面模的存在条件,并发现:界面模的存在仅取决于界面耦合作用,与横向自旋波无关.     

体单轴各向异性对双层铁磁薄膜中自旋波共振谱的影响

重点研究了双层铁磁薄膜系统在层间反铁磁耦合下,体单轴各向异性对自旋波色散关系和共振谱的影响.结果表明:随着体单轴各向异性常数的增加,各类型模之间相互转化;高能禁闭模共振减弱,低能禁闭模和界面模共振增强.     

磁场对体心立方双层铁磁性薄膜中的自旋波能谱的影响

采用界面重参数化方法,在周期性边界条件下严格求解了界面铁磁耦合的体心立方异质型双层铁磁性薄膜自旋波本征值问题,研究了两层薄膜中自旋波能带结构.在此基础上重点讨论了垂直于膜面的外加磁场对自旋波能带结构的影响,结果表明,磁场对自旋波的能带结构有很大的影响,足够大的磁场可以使体模消失.     

耦合有限铁磁性自旋链中的界面自旋波及其存在条件

本文采用界面重标度方法，严格地求解了两个有限铁磁住自旋链层间为铁磁耦合的界面自旋波的本征值问题．获得了严格的和完全解析的界面自旋波的充要条件．     

三层不对称铁磁膜中的自旋波界面模

研究了Ａ、Ｂ、Ｃ三层不对称铁磁膜,并利用界面重标度方法求解了自旋波的低能量子本征问题,得到了自旋波界面模。数值计算表明,当各层自旋相同时,只要各层的交换作用常数ＪＡ、ＪＢ、ＪＣ相差不大,     

A-B-A系统界面各相异性与声学型界面自旋波存在条件

计入外磁场、铁磁和反铁磁层间耦合、体和界面各向异性后,研究了Ａ－Ｂ－Ａ三链系统中物声学型界面自旋波及其存在条件,结果发现,在此系统中,存在奇、偶两种不同宇称的声学型界面自旋波,在没的界面各向异性条件,这两种声学型界面自旋波解的个数分别在０￣２之间变化。     

外磁场对铁磁双层膜自旋波能带的影响

研究了在外磁场作用下铁磁双层薄膜材料中自旋波的本征值问题.采用界面重参数化方法,在周期性边界条件下,严格求解系统的三种本征模,并给出横向自旋波取全部值的能带结构图,讨论了外磁场对自旋波能带的影响.     

Effect of the Interface Anisotropy on Optical Interface Spin Waves in an A-B-A System

计入外磁场、体和界面单轴各向异性后，研究了铁磁和反铁磁层间耦合的Ａ－Ｂ－Ａ三链系统中的光学界面自旋波及其存在的充要条件．结果发现，在三链系统中，有两种不同类型的光学界面自旋波，它们在不同界面各向异性条件下，均可存在０～２个自旋波解     

Magnetoresistance of the thin film ferromagnetic nanoconstrictions

The magnetoresistance and I-V characteristics at different temperatures of the thin film ferromagnetic nanoconstrictions of variable width (from 20 to 250 nm) and 10 nm thicknesses, fabricated by electron beam lithography and vacuum thin film deposition are compared. The magnetoresistance and resistance of the thin film ferromagnetic nanoconstrictions are not related to the width of the nanoconstrictions. Instead the resistance of the local nano-region in the middle of the thin film ferromagnetic nanoconstriction has only a minor role compared to that of the two microscale thin film ferromagnetic electrodes, which contribute the majority of the measured resistance. The magnetoresistances of the thin film ferromagnetic nanoconstrictions and a 0.2 cm × 0.8 cm thin ferromagnetic film deposited under the same conditions were also compared; the thin film ferromagnetic nanoconstrictions have higher magnetoresistances than the thin ferromagnetic film, which implies that the measured magnetoresistance of the thin film ferromagnetic nanoconstrictions comes mainly from the local nano-region in their centers. In conclusion, the measured magnetoresistance of the whole sample is similar to the anisotropic magnetoresistance, because the resistance of the two microscale thin film ferromagnetic electrodes is much higher than that of the local nano-region in the middle of the samples. Comparing the experimental results for the thin film ferromagnetic nanoconstrictions and the thin ferromagnetic film reveals that the magnetoresistance of the local nano-region in the middle of the sample is much higher than that of the two microscale thin film ferromagnetic electrodes attached to it.     

Magnetoresistance of the ferromagnetic nanocontacts fabricated by electrodeposition

A "T" shaped micro-gap was fabricated by mechanical polishing between two Cu film electrodes on the surface of single-sided bonded copper.A nano-gap was then fabricated in the prepared micro-gap by resistance feedback controlled electroplating.Finally Ni 80 Fe 20 ferromagnetic nanocontacts of several sizes were fabricated in the prepared nano-gap by resistance feedback controlled electroplating.The magnetoresistance of each Ni 80 Fe 20 ferromagnetic nanocontact was not related to its size.Fabrication of the Ni 80 Fe 20 ferromagnetic nanocontacts in the nano-gap can reduce the contribution of magnetostriction to the magnetoresistance.The magnetoresistance values of the Ni 80 Fe 20 ferromagnetic nanocontacts were as high as those of the Ni ferromagnetic nanocontacts.This implies that the contribution of magnetostriction to the ballistic magnetoresistance of the ferromagnetic nanocontacts can be neglected.The ferromagnetic nanocontacts fabricated in this study,and in other cases,have two anisotropic interfaces on the sides of the nanocontacts.However,the magnetic field can alter the contribution of the interaction between the two anisotropic interfaces to the ballistic magnetoresistance of the ferromagnetic nanocontacts,and this effect can not be ruled out yet.     

铁磁颗粒夹杂软基体复合材料的制备和特性分析

目的制备铁磁颗粒夹杂软基体复合材料,研究其磁学特性和力学特性。方法在室温条件下采用自然固化制备得到铁磁颗粒夹杂软基体复合材料。利用多物理场COMSOL有限元分析软件,研究单向磁场和单轴拉伸下颗粒体积分数对各向异性及各向同性的铁磁颗粒夹杂软基体复合材料特性的影响。结果颗粒体积分数对2种复合材料的相对磁导率及杨氏模量影响很大,且相同颗粒体积分数时,各向异性的铁磁颗粒夹杂软基体复合材料受颗粒体积分数影响更大。结论铁磁颗粒夹杂软基体复合材料的有效性能不仅和材料各组分的比例有关,而且和材料各组分的分布形式有很大关系。     

A—B—A三链系统层间耦合与界面自旋波存在条件

研究磁场中具有单轴各向异性的Ａ－Ｂ－Ａ结构自旋链中的界面自旋波及其存在条件。详细讨论了外场等物理因素对存在条件的影响。     

铁磁共振下磁各向异性材料的负折射特性研究

利用Landau-Lifshitz-Gilbert模型理论计算了铁磁共振条件下天然材料锰钙钛矿薄膜的张量磁导率,发现铁磁共振能够获得负的磁导率,而锰钙钛矿材料特有的庞磁电阻效应可以得到负的介电常数,这使得负折射率成为可能.结合麦克斯韦方程组,分析了铁磁共振时材料的微波传播特性.研究结果表明,在外磁场下天然锰钙钛矿材料不仅可以获得负折射率,更重要的是负折射的工作频率受到了外磁场强弱的调制,材料具备了可调谐特性.     

各向异性铁磁双层薄膜中的界面自旋波及存在条件

研究了各向异性铁磁双层薄膜中的界面自旋波的本征值问题，获得了界面自旋波存在的充要条件。数值计算结果表明，临界值ＪＡＢ＾Ｃ随各向异性参数的比值增大而单调增加，且当链长（格点数）为十几个格点时变为耦合半无限自旋链的结果。