Charge Ordering Due to Magnetic Symmetry Breaking

Abstract

It is argued that both transitions observed in 50%-doped manganites, at the N\'{e}el temperature ($T_{\rm N}$) and the so-called charge ordering temperature ($T_{\rm CO}$), are magnetic. $T_{\rm N}$ corresponds to the order-disorder transition, which takes place between ferromagnetic zigzag chains, while the coherent motion of spins within the chains is destroyed only around $T_{\rm CO}$. The magnetic structure realized below $T_{\rm CO}$ is highly anisotropic. It is dressed by the lattice distortion and leads to huge anisotropy of the electronic structure, which explains stability of this state as well as the form of charge-orbital pattern above $T_{\rm N}$. The type of phase transition at $T_{\rm N}$ depends on lattice interactions.