Magnetic correlations in manganites

Journal Article · Wed Sep 01 04:00:00 EDT 1999 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.60.7911· OSTI ID:686460

Schlottmann, P ^[1]

---

1. Department of Physics, Florida State University, Tallahassee, Florida 32306 (United States)

Manganese ions in a mixed-valent state of two magnetic configurations, Mn{sup 4+} and Mn{sup 3+}, play an important role in the magnetoresistance of LaMnO{sub 3}-based systems. We describe each Mn ion with the Mn{sup 4+} represented by a spin S=3/2 (three localized {ital d} electrons in the t{sub 2g} orbitals with their spins ferromagnetically coupled) and the Mn{sup 3+} configuration having an additional localized 3d-e{sub g} electron to form a total spin (S+1/2). The e{sub g} electron hybridizes with conduction electrons (representing the crystal) and the multiple occupancy of the e{sub g} level is excluded at each site by a large Coulomb energy. We consider a cubic cluster of eight such manganese ions and allow a directed hopping of the e{sub g} electrons between the Mn sites. Hence, bonding and antibonding levels are formed giving rise to the ferromagnetic double-exchange mechanism, which competes with the antiferromagnetic superexchange between the t{sub 2g} spins of the ions. The spins {ital S} are oriented in the magnetic configurations of the {ital A}, {ital C}, and {ital G} phases. In the intermediate valent regime we calculate the ground-state energy, the valence, the population of the various bonding and antibonding resonant levels, the charge susceptibility, the quadrupolar susceptibility, and the response to a charge imbalance between the sites of two {open_quotes}sublattices{close_quotes} as a function of the energy of the e{sub g} level using a mean-field slave-boson formulation. The susceptibilities are a measure for the coupling to phonons, i.e., the formation of small polarons, Jahn-Teller distortions, and charge order, respectively. A crossover between groundstates with different spin configurations is found as a function of the e{sub g} level energy for reasonable model parameters. {copyright} {ital 1999} {ital The American Physical Society}

• OSTI ID: 686460
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 11 Vol. 60; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANTIFERROMAGNETIC MATERIALS
BONDING
ELECTRONIC STRUCTURE
EXCHANGE INTERACTIONS
FERROMAGNETIC MATERIALS
GROUND STATES
JAHN-TELLER EFFECT
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
MAGNETIC SUSCEPTIBILITY
MAGNETORESISTANCE
MANGANESE OXIDES
POLARONS
VALENCE