Magnetic form factor Kondo systems: Kondo moment reduction versus conduction electron polarization
✍ Scribed by E. Pavarini; L.C. Andreani; G. Amoretti
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 231 KB
- Volume
- 206-207
- Category
- Article
- ISSN
- 0921-4526
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✦ Synopsis
A theory for the magnetic form factor in Kondo systems is presented which allows us to distinguish Kondo reduction of the moments from conduction electron polarization effects. The sign of the deviations of the form factor at small scattering vector is ascribed to the dominance of a superexchange-like contribution to the conduction electron polarization, which is contained in the Anderson model in addition to the usual RKKY polarization.
Kondo behaviour is known to co-exist with long range magnetic order in reduced-moments compounds. The most complete information about static magnetic properties of ordered systems is provided by polarized neutron elastic scattering, which allows us to measure the magnetic form factor (FF), i.e. the Fourier transform of the magnetization density. The FF gives the possibility of separating conduction electron ('delocalized') from 4f electron ('localized') contributions to the magnetization density; at small scattering vector q, the FF yields the total (localized + delocalized) magnetic moment, whereas at large q only the localized moment is observed [1,2].
In normal rare earth systems (as in the series REAl 2, RE = Nd, Sm, Gd, Ho) [1], the experimental form factor is uniformly reduced with respect to the free ion one, due to crystal field (CEF) effects. At small q, the FF deviates from the values expected for the ion in the CEF, due to a Ruderman Kittel Kasuya Yosida (RKKY) spin polarization of conduction electrons. The total polarization is (s~)=(3OnJ~f/