Double-exchange mechanism

The double-exchange mechanism is a type of a magnetic exchange that may arise between ions in different oxidation states.

First proposed by Clarence Zener,[1] this theory predicts the relative ease with which an electron may be exchanged between two species and has important implications for whether materials are ferromagnetic, antiferromagnetic, or exhibit spiral magnetism.

At the end of the process, an electron has moved between the neighboring metal ions, retaining its spin.

The double-exchange predicts that this electron movement from one species to another will be facilitated more easily if the electrons do not have to change spin direction in order to conform with Hund's rules when on the accepting species.

[citation needed] Hence the overall energy saving can lead to ferromagnetic alignment of neighboring ions.

An example of double exchange in the compound $La_{1-x}A_{x}MnO_{3}$ . The exchange involves the outermost orbitals for each atom, which are 3d ⁴ for Mn ³⁺ , 3d ³ for Mn ⁴⁺ , and 2p ⁶ for the O ^2- . Here e _g and t _2g are crystal field theory notation for the octahedral splitting of the d-orbitals.