摘要翻译：
最近有人提出，交换弹簧介质提供了一种在不引起热不稳定性（超顺磁性）的情况下增加介质密度的方法，它使用由交换耦合的硬层和软层。Victora提出了一个品质因数xi=2E_b/mu_0M_sH_sw，即同开关场的Stoner-Wohlfarth系统的能垒之比，对于Stoner-Wohlfarth（相干开关）粒子为1，对于最佳两层复合介质为2。许多理论方法已经被用来解决这个问题（例如，各种数量的耦合Stoner-Wohlfarth层和连续微磁学）。在本文中，我们证明了这些方法中的许多可以看作是问题的变分形式的特例或近似，在变分形式中，能量在固定磁化强度下是最小的。结果可以用能量随磁矩m_z的变化曲线直观地显示出来，其中开关场[最大斜率E(m_z)]和稳定性（由能垒E_b决定）在几何上都是可见的。在这个公式中，我们可以证明功绩xi的严格限制，它不能高于4。我们还证明了Suess等人提出的二次不istpy非常接近这个极限。
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英文标题：
《Domain wall switching: optimizing the energy landscape》
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作者：
Zhihong Lu, P. B. Visscher, and W. H. Butler
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最新提交年份：
2007
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分类信息：

一级分类：Physics        物理学
二级分类：Statistical Mechanics        统计力学
分类描述：Phase transitions, thermodynamics, field theory, non-equilibrium phenomena, renormalization group and scaling, integrable models, turbulence
相变，热力学，场论，非平衡现象，重整化群和标度，可积模型，湍流
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一级分类：Physics        物理学
二级分类：Materials Science        材料科学
分类描述：Techniques, synthesis, characterization, structure.  Structural phase transitions, mechanical properties, phonons. Defects, adsorbates, interfaces
技术，合成，表征，结构。结构相变，力学性质，声子。缺陷，吸附质，界面
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英文摘要：
  It has recently been suggested that exchange spring media offer a way to increase media density without causing thermal instability (superparamagnetism), by using a hard and a soft layer coupled by exchange. Victora has suggested a figure of merit xi = 2 E_b/mu_0 m_s H_sw, the ratio of the energy barrier to that of a Stoner-Wohlfarth system with the same switching field, which is 1 for a Stoner-Wohlfarth (coherently switching) particle and 2 for an optimal two-layer composite medium. A number of theoretical approaches have been used for this problem (e.g., various numbers of coupled Stoner-Wohlfarth layers and continuum micromagnetics). In this paper we show that many of these approaches can be regarded as special cases or approximations to a variational formulation of the problem, in which the energy is minimized for fixed magnetization. The results can be easily visualized in terms of a plot of the energy as a function of magnetic moment m_z, in which both the switching field [the maximum slope of E(m_z)] and the stability (determined by the energy barrier E_b) are geometrically visible. In this formulation we can prove a rigorous limit on the figure of merit xi, which can be no higher than 4. We also show that a quadratic anistropy suggested by Suess et al comes very close to this limit.
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PDF链接：
https://arxiv.org/pdf/704.0913