RKKY interaction
In the
Malvin Ruderman and Charles Kittel of the
Tadao Kasuya from Nagoya University later proposed that a similar indirect exchange coupling could occur with localized inner d-electron spins instead of nuclei.[2] This theory was expanded more completely by Kei Yosida of the UC Berkeley, to give a Hamiltonian that describes (d-electron spin)–(d-electron spin), (nuclear spin)–(nuclear spin), and (d-electron spin)–(nuclear spin) interactions.[3] J.H. Van Vleck clarified some subtleties of the theory, particularly the relationship between the first- and second-order perturbative contributions.[4]
Perhaps the most significant application of the RKKY theory has been to the theory of giant magnetoresistance (GMR). GMR was discovered when the coupling between thin layers of magnetic materials separated by a non-magnetic spacer material was found to oscillate between ferromagnetic and antiferromagnetic as a function of the distance between the layers. This ferromagnetic/antiferromagnetic oscillation is one prediction of the RKKY theory.[5][6]
References
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Further reading
- Blandin, A.; Friedel, J. (1959). "Propriétés magnétiques des alliages dilués. Interactions magnétiques et antiferromagnétisme dans les alliages du type métal noble-métal de transition". Journal de Physique et le Radium. 20 (2–3): 160. .