共查询到20条相似文献,搜索用时 62 毫秒
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金属薄膜中的量子尺寸效应 总被引:1,自引:0,他引:1
运用最子统计的方法,计算金属薄膜中电子的态密度、电子密度、弛豫时间、计算结果表明:这些物理量都是金属薄膜厚度的函数,且随着薄膜厚度作周期性振荡。 相似文献
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采用基于火炮加载的三样品精细波剖面对比测量,研究了晶向效应对铁弹-塑性转变及体心立方结构(bcc,α相)至六角密排结构(hcp,ε相)相变特性的影响.观测到单晶铁异常的弹-塑性转变行为,这与基于位错密度描述的黏塑性本构模型计算结果相符,对应的Hugoniot弹性极限δ_(HEL)均大于6 GPa,且具有晶向相关性,即δ(111)/(HEL)δ(110)/(HEL)δ(100)/(HEL);系统获取了相变起始压力P_(PT)晶向相关性的实验数据,[100],[110]和[111]晶向的PPT实测值分别为13.89±0.57 GPa,14.53±0.53 GPa,16.05±0.67 GPa,其变化规律与非平衡分子动力学计算结果相符.上述结果揭示出冲击压缩下单晶铁存在塑性与相变微观机理的强耦合,为完善用于冲击实验描述的相场动力学模型提供了重要的实验支撑. 相似文献
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在关联有效场理论的框架内, 利用微分算子技术, 详细地计算了基于横场伊辛模型描述的对称铁电薄膜系统的相变性质. 根据薄膜各层自旋平均值构成的一系列耦合方程, 推导出可以用来计算任意层的具有不同表面层的薄膜相图的解析通式方程, 讨论了参数修改对薄膜相互作用参数从FPD (铁电相占主导地位的相图)到PPD (顺电相占主导地位的相图)过渡值和参数空间中各相变区域的影响. 在与平均场近似进行比较的结果显示, 关联有效场理论所得到的铁电薄膜的铁电性在某种程度上比平均场近似下的结果减弱.
关键词:
铁电薄膜
横场伊辛模型
相图
居里温度 相似文献
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基于Laudau-Devonshire的热动力学模型, 计算了EuTiO3铁电薄膜材料的电热效应. 结果显示在外加应力的调控下, 电极化、电热系数以及绝热温差都会随之变化. 外加垂直于表面的张应力加大, 薄膜的相变温度升高, 绝热温差增加, 最大绝热温差所对应的工作温度向高温区移动. 对于二维平面失配应变um =-0.005的薄膜, 当外加张应力σ3 = 5 GPa时, 其最大电热系数为1.75×10-3 C/m2·K, 电场变化200 MV/m 时室温下绝热温差ΔT 的最大值可达到14 K 以上, 绝热温差ΔT ≥13 K 的工作温区超过120 K, 表明可以通过调控外部应力来获取室温时较大的绝热温差. 此结果预示着铁电EuTiO3 薄膜在室温固态制冷方面可能具有较好的应用前景. 相似文献
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Epitaxy surface effect on the first-order phase transition properties in a ferroelectric thin film
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By modifying the interchange interactions and the transverse fields on the epitaxy surface layer,this paper studies the phase transition properties of an n-layer ferroelectric thin film by the Fermi-type Green’s function technique based on the transverse Ising model with a four-spin interaction.The special attention is given to the effect of the epitaxy surface layer on the first-order phase transition properties in the parameter space constructed by the ratios of the bulk transverse field and the bulk four-spin interaction to the bulk two-spin interaction with the framework of the higher-order decoupling approximation to the Fermi-type Green’s function.The results show that the first-order phase transition properties will be changed significantly due to the modification of interchange interaction and transverse field parameters on the epitaxy surface layer.The dependence of the first-order phase transition properties on the thickness of ferroelectric thin films is also discussed. 相似文献
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采用热力学非线性理论,研究了外加电场对立方基底Pb(Zr0.3Ti0.7)O3(PZT)铁电薄膜相变的影响.通过数值计算,得到了"失配应变-外加电场"相图,及外加电场与极化强度的关系.当外加电场达到186 kV/cm时,能使生长在SrTiO3 基底上PZT铁电薄膜从单斜r相转变为c相.在实验上,采用扫描探针显微镜通过对PZT薄膜施加不同的极化电场来研究了它的电畴翻转.从得到的压电响应相图可以看出,绝大多数的电畴是清晰可
关键词:
铁电薄膜
相变
扫描探针显微镜
失配应变 相似文献
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Combined effect of the transition layer and interfacial coupling on the properties of ferroelectric bilayer film
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Within the framework of modified Ginzburg--Landau--Devonshire
phenomenological theory, a ferroelectric bilayer film with a
transition layer within each constituent film and an interfacial
coupling between two materials has been studied. Properties
including the Curie temperature and the spontaneous polarization of
a bilayer film composed of two equally thick ferroelectric
constituent films are discussed. The results show that the combined
effect of the transition layer and the interfacial coupling plays an
important role in explaining the interesting behaviour of
ferroelectric multilayer structures consisting of two ferroelectric
materials. 相似文献
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Effect of misfit strain on the electrocaloric effect of polydomain epitaxial ferroelectric thin films
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The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTiO 3 thin films at room temperature is investigated using the Ginzburg-Landau-Devonshire thermodynamic theory. Numerical calculations indicate that the misfit strain has a large impact on the ferroelectric polarization states and the electrocaloric effect. Most importantly, the electrocaloric effect in the polydomain ca 1 /ca 2 /ca 1 /ca 2 phase is much larger than that in the monodomain c phase and the other polydomain phases. Consequently, a large electrocaloric effect can be obtained by carefully controlling the misfit strain, which may provide potential applications in refrigeration devices. 相似文献
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Raman scattering investigation of phase transition in the ferroelectric Ba0.95Ca0.05TiO3 is reported. The results suggest onset of significant dynamic disorder at 105°C. This corroborates findings of recent structural
study regarding large positional disorder associated with Ti and O1 atoms well below the tetragonal to cubic transition temperature
(∼150°C). 相似文献
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Influence of lateral size on dielectric properties of ferroelectric thin films with structure transition zones
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By taking into account structural transition zones near the lateral
and thickness direction edges, this paper uses a modified transverse
Ising model to study dielectric properties of a finite size
ferroelectric thin film in the framework of the mean-field
approximation. The results indicate that the influence of the
lateral size on the dielectric susceptibility cannot be neglected
and lateral structural transition zones could be a crucial factor
that improves the mean susceptibility of the fixed size film. 相似文献
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The size effects of the critical behaviors for the systems of interacting spins are discussed extensively in literature. In this paper, the finite-size dependence of the critical temperature and susceptibility of the ferroelectric thin film are investigated numerically based on the four-state Potts model with the nearest-neighbor interactions between the dipole moments. The four orientations of the domains exist in the ferroelectric film and the movement of the domain walls determines the polarization switching process besides the boundary conditions of the film. The critical exponents are obtained and our investigations show that the boundary conditions play the important roles for the ferroelectric properties of the thin films and the critical behavior of the thin films strongly depends on the feature of the surface. 相似文献
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The size effects of the critical behaviors for the systems of
interacting spins are discussed extensively in literature. In this
paper, the finite-size dependence of the critical temperature and
susceptibility of the ferroelectric thin film are investigated
numerically based on the four-state Potts model with the
nearest-neighbor interactions between the dipole moments. The four
orientations of the domains exist in the ferroelectric film and the
movement of the domain walls determines the polarization switching
process besides the boundary conditions of the film. The critical
exponents are obtained and our investigations show that the boundary
conditions play the important roles for the ferroelectric
properties of the thin films and the critical behavior of the thin
films strongly depends on the feature of the surface. 相似文献