Hybridization impurity model for Mn ions

Journal Article · Fri May 01 04:00:00 EDT 1998 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.57.10630· OSTI ID:627836

Schlottmann, P ^[1]

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1. Department of Physics, Florida State University, Tallahassee, Florida32306 (United States)

Manganese ions are believed to play an important role in the magnetoresistance of LaMnO{sub 3}-based systems. We consider a Mn impurity in the mixed-valence state of the two magnetic configurations Mn{sup 4+} and Mn{sup 3+}. The Mn{sup 4+} is represented by a spin S=3/2 consisting of three localized d electrons in the t{sub 2g} orbitals with their spins ferromagnetically coupled to maximize the total spin. The Mn{sup 3+} configuration has an additional localized d electron in one of the e{sub g} orbitals to form a total spin S+1/2. The e{sub g} electron hybridizes with the conduction electrons and the multiple occupancy of the e{sub g} level is excluded by a large Coulomb energy. This gives rise to a quadrupolar Kondo effect, which compensates for the orbital degrees of freedom into a quadrupolar singlet. We study the lifting of the degeneracy of the e{sub g} levels due to a small quadrupolar field, which is related to the local Mn-O bond lengths. In the spin-polarized limit (ferromagnetic lattice) the model is solved exactly. In a small magnetic field the underscreening of the spin via the usual Kondo effect interferes with the quadrupolar Kondo effect, yielding an enhanced Kondo temperature. The quadrupolar susceptibility gradually increases with the magnetic field, as a consequence of the breaking up of the spin compensation. {copyright} {ital 1998} {ital The American Physical Society}

• OSTI ID: 627836
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 17 Vol. 57; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BOND LENGTHS
FERROMAGNETIC MATERIALS
HYBRIDIZATION
IMPURITIES
KONDO EFFECT
LANTHANUM OXIDES
MAGNETIC SUSCEPTIBILITY
MAGNETORESISTANCE
MANGANESE IONS
MANGANESE OXIDES