Recent experimental studies performed in the normal state of iron-based superconductors have discovered the existence of the C₄-symmetric (tetragonal) itinerant magnetic state. This state can be described as a spin density wave with two distinct magnetic vectors Q→1 and Q→2. Given an itinerant nature of magnetism in iron-pnictides, we develop a quasiclassical theory of tetragonal magnetic order in disordered three-band metal with anisotropic band structure. Within our model we find that the C₄-symmetric magnetism competes with the C₂-symmetric state with a single Q→ magnetic structure vector. Our main results is that disorder promotes tetragonal magnetic state which is in agreement with earlier theoretical studies.

在铁基超导体的正常状态下进行的最新实验研究发现，铁基超导体的存在 C₄对称（四边形）迭代磁状态。这种状态可以描述为具有两个不同磁矢量的自旋密度波问→1个 和 问→2。考虑到铁中的磁性具有流动性，我们开发了具有各向异性能带结构的无序三能带金属中四方磁性阶的准经典理论。在我们的模型中，我们发现C₄对称磁性与C_2个对称状态问→磁性结构矢量。我们的主要结果是，无序促进了四方磁性态，这与早期的理论研究是一致的。