Effect of lattice distortions on the competition between the double and superexchange mechanisms in LaMnO{sub 3}

Journal Article · Mon Sep 01 04:00:00 EDT 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.56.7255· OSTI ID:664507

Mryasov, O N ^[1]; Sabiryanov, R F ^[2]; Freeman, A J ^[1]; Jaswal, S S ^[2]

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1. Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States)
2. Center for Materials Research and Analysis, and Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588-0111 (United States)

Double exchange (DE), superexchange (SE), and higher-order contributions to the exchange interaction energy between Mn layers in LaMnO{sub 3} are studied using the linear-muffin-tin-orbital method as generalized to treat noncollinear magnetic configurations. The degree of the internal lattice distortion (f) and the angle ({theta}) between ferromagnetically ordered Mn layers are considered as simulation parameters. We find that both global and internal lattice distortions dramatically influence the character of the exchange interactions: global distortions associated with variations of the apical Mn-O bond length promotes the DE contribution; the bending of the Mn-O bonds in the (a-b) plane suppresses the DE and promotes the antiferromagnetic SE contribution to the interlayer exchange energy. Overall, the character of exchange interactions is determined by SE contributions: in hypothetical ferromagnetic phases DE interactions mediated by itinerant electrons is present but still rather small compared with SE; in antiferromagnetic phases this DE is negligible and non-Heisenberg terms are small compared with SE. We find further that a metal-to-semiconductor transition (in the sense of a band-gap opening) occurs in the range of parameters of magnetic and lattice distortion variations given by {theta}{ge}120{degree} and f{ge} 0.7. {copyright} {ital 1997} {ital The American Physical Society}

• DOE Contract Number: FG02-86ER45262; FG02-88ER45372
• OSTI ID: 664507
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 12 Vol. 56; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANTIFERROMAGNETIC MATERIALS
BOND LENGTHS
CHEMICAL BONDS
CRYSTAL LATTICES
ELECTRONIC STRUCTURE
ENERGY GAP
EXCHANGE INTERACTIONS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
MAGNETIC PROPERTIES
MANGANESE OXIDES
MUFFIN-TIN POTENTIAL