Superexchange or Kramers—Anderson superexchange is the strong usually antiferromagnetic coupling between two next-to-nearest neighbour cations through a non-magnetic anion. In this way, it differs from direct exchange in which there is coupling between nearest neighbor cations not involving an intermediary anion. Superexchange superexchange ferromagnetic liquid a result of the electrons having come from the superexchange ferromagnetic liquid donor atom and being coupled with the receiving ions' spins.
If the two next-to-nearest neighbor positive ions are connected at 90 degrees to the bridging non-magnetic anion, then the interaction can be a ferromagnetic interaction. Superexchange was proposed by Hendrik Kramers in when he noticed that in crystals like MnO, there are Mn atoms that interact with one another despite having nonmagnetic oxygen atoms between them Fig.
A set of semi-empirical rules were developed by John B. Goodenough and Junjiro Kanamori in the s. They are based on the symmetry relations and electron occupancy of the overlapping atomic orbitals assuming the localized Heitler—London, or valence-bond, model is more representative of the chemical bonding than is the delocalized, or Hund—Mulliken—Bloch, model. Essentially, the Pauli exclusion principle dictates that between two magnetic ions with superexchange ferromagnetic liquid orbitals, which couple through an intermediary non-magnetic ion e.
The coupling between an ion with either a half-filled or filled orbital and one with a vacant orbital can be either antiferromagnetic or ferromagnetic, but superexchange ferromagnetic liquid favors ferromagnetic. Complications begin to arise in various situations: Double exchange is a related magnetic coupling interaction proposed by Clarence Zener to account for electrical transport properties.
It differs from superexchange in the following manner: For other occupations double exchangethe electrons are itinerant delocalized ; this results in the material displaying magnetic exchange coupling as superexchange ferromagnetic liquid as metallic conductivity. The p orbitals from oxygen and d orbitals from manganese superexchange ferromagnetic liquid form a direct exchange.
There is antiferromagnetic order because the singlet state is energetically favoured. This configuration allows a delocalization of the involved electrons due to a lowering of the kinetic energy. From Wikipedia, the free encyclopedia. Kramers, Physica 1, Solids 6, Solids 10, 87 Cleary "Principles of Inorganic Materials Design," 2nd ed.
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