长程库仑作用下双交换磁体中的非均匀相
Inhomogeneous Phases in a Double-Exchange Magnet with Long Range Coulomb Interactions
摘要：
我们考虑一个模型与竞争的双交换（铁磁）和超交换（反铁磁）的相互作用的制度，发生相分离。长程库仑相互作用的存在阻碍了宏观相分离，并有利于微观不均匀的配置。我们使用变分Hartree-Fock方法，结合蒙特卡罗模拟来研究二维系统中这种构型的几何结构。我们发现，一个钻石形的铁磁液滴阵列是在低电子密度的首选配置，而交替的铁磁和反铁磁的对角线条纹出现在较高的密度。这些发现预计将是相关的薄膜的巨磁阻锰氧化物。
英文摘要：
We consider a model with competing double-exchange (ferromagnetic) and super-exchange (anti-ferromagnetic) interactions in the regime where phase separation takes place. The presence of a long range Coulomb interaction frustrates a macroscopic phase separation, and favors microscopically inhomogeneous configurations. We use the variational Hartree-Fock approach, in conjunction with Monte-Carlo simulations to study the geometry of such configurations in a two-dimensional system. We find that an array of diamond shaped ferromagnetic droplets is the preferred configuration at low electronic densities, while alternating ferromagnetic and anti-ferromagnetic diagonal stripes emerge at higher densities. These findings are expected to be relevant for thin films of colossal magneto-resistive manganates.
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