Spatial structures of the intermediate state between superconductivity and ferromagnetism
Spatial structures of the intermediate state between superconductivity and ferromagnetism
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超导与铁磁性中间态的空间结构
DOI：
10.3929/ethz-a-000347104
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
P. Stampfli
中科院分区：
文献类型：
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作者：
P. Stampfli
铁磁超导体在低温下是超导的，但在一定温度以下，它们变成铁磁的，超导性被破坏，在中间态，超导性和铁磁性共存.我们用广义的布尔格朗道平均场模型来描述超导性、磁化强度和它们之间的竞争.超导和磁化之间存在电磁相互作用和交换相互作用。电磁相互作用是由于有序磁矩的磁场，其大到足以破坏超导性。超导和磁化的共存只有通过空间结构才成为可能。只有电磁相互作用才能始终包含在平均场模型中。交换相互作用被近似处理。电磁相互作用具有很强的非定域性，可以产生非常复杂的结构，大多数理论家只考虑了磁化或超导的空间结构，而没有考虑两者的空间结构，我们研究了结合了超导和磁化的联合收割机拓扑结构的新结构.它们是从简单结构的不稳定性发展而来的，因为它们不能直接被发现。材料的磁各向异性变得很重要。我们分别处理易轴和易面各向异性。求解Ginzburg朗道方程是一个困难且数值上不稳定的问题.我们利用每个结构的对称性来表征序参数，直接寻找自由能的最小值.这是数值上稳定且定义明确的.我们得到了具有不同自由能最小值的结构.提出了一种适用于易平面磁各向异性材料ErRh. B.具有特别有趣的性质。磁化强度的一个分量周期性地分成大的相反的畴。每个畴包含一行极性相反的涡旋线或反涡旋线。磁化强度在布洛赫壁中并不消失。相反，存在一个磁化强度，
Ferromagnetic superconductors are superconducting at low temperatures, but below a certain temperature they become ferromagnetic and the super¬ conductivity breaks down.In an intermediate State coexistence of super¬ conductivity and ferromagnetism is observed.We use a generalized Ginz¬ burg Landau mean field model to describe the superconductivity,the magnetization and their mutual competition. There is an electromagnetic and an exchange interaction between super¬ conductivity and magnetization.The electromagnetic interaction is due to the magnetic field of the ordered magnetic moments which is large enough to destroy superconductivity.Coexistence of superconductivity and magnetization becomes only possible through spatial structure.Only the electro¬ magnetic interaction can be included consistently in the mean field model.The exchange interaction is treated approximately. The electromagnetic interaction has a very nonlocal character and can give rise to very complicated structures.Most theorists have only considered spatial structure in either the magnetization or the supercon¬ ductivity but not in both together.We examine new structures which combine topological structure in both superconductivity and magnetization. They are developed from instabilities of simpler structures as they cannot be found directly.The magnetic anisotropy of the material becomes important.We treat easy axis and easy plane anisotropy separately. To solve the Ginzburg Landau equations is very difficult and numerically instable.Instead.we use for each structure its symmetries to characterize the order parameters and directly search for the minimum of the free energy.This is numerically stable and well defined.We obtain structures which are distinct minima of the free energy. A new alternating vortex lattice structure for materials with easy plane magnetic anisotropy such as ErRh.B. has especially interesting properties.One component of the magnetization is periodically devided into large opposite domains.Each domain contains one row of vortex lines or antivortex lines with opposite polarity.The magnetization does not vanish in the Bloch walls.instead there is a magnetization which is