Stoner model

The Stoner model (also called collective electron model by Stoner) is a model named after the physicist Edmund Clifton Stoner (1899–1968) to describe the ferromagnetism of the metals iron, nickel and cobalt as an effect of the interaction via (freely moving) ribbon electrons. It is a simplistic, phenomenological model and was first developed by Stoner in 1939.

In the Stoner model, the band structure is divided into a spin-up and a spin-down orientation. In the case of a ferromagnet , the two spin components are energetically shifted against each other. Although this shift increases the kinetic energy , the exchange interaction also generates potential energy , so that overall an energy gain can be achieved. For this, the exchange interaction (coupling constant ) must be large and the density of states close to the Fermi energy must be high (Stoner criterion): ${\displaystyle J}$ ${\displaystyle E_{\text{F}}}$

${\displaystyle JN(E_{\text{F}})>1}$.

It should not be confused with the Stoner-Wohlfarth model by Stoner and Erich Peter Wohlfarth (1948), which describes the magnetization of an ensemble of randomly oriented small ferromagnetic single-domain crystals. Since Wohlfarth as a student of Stoner also used the Stoner model a lot, the model is sometimes also linked to his name in German-speaking countries.

literature

• Harald Ibach, Hans Lüth: Solid State Physics . 7th edition Springer, Berlin 2009, ISBN 978-3-540-85794-5 .

Individual evidence

1. ↑ EC Stoner: Collective Electron Ferromagnetism. II. Energy and Specific Heat. In: Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 169, 1939, p. 339, doi : 10.1098 / rspa.1939.0003 .
2. ↑ E. Kneller, S. Methfessel, D. Wagner: Obituary for Erich Peter Wohlfarth. In: Physics Journal. 44, 1988, p. 178, doi : 10.1002 / phbl.19880440613 . PDF . In Ibach / Lüth, Solid State Physics, both are named as the originators of the model.