Single valence and structural order in the colossal-magnetoresistant pyrochlore Tl{sub 2}Mn{sub 2}O{sub 7}

Journal Article · Wed Jan 01 04:00:00 EST 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.55.R688· OSTI ID:439048

Kwei, G H ^[1]; Booth, C H; Bridges, F ^[2]; Subramanian, M A ^[3]

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1. Chemistry and Materials Sciences Department, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2. Physics Department, University of California, Santa Cruz, California 95064 (United States)
3. Dupont Central Research and Development, Experimental Station, Wilmington, Delaware 19880 (United States)

Without Mn{sup 3+}/Mn{sup 4+} mixed-valence or Jahn-Teller distortions in the MnO{sub 6} octahedra, the origin of colossal magnetoresistance (CMR) in the pyrochlore Tl{sub 2}Mn{sub 2}O{sub 7} is thought to arise instead from superexchange with large incoherent scattering near the ferromagnetic transition. Using x-ray-absorption spectroscopy, we have shown that the electronic state of Tl is nearly identical to that in Tl{sub 2}O{sub 3}, indicating doping into the Tl6s bands, that there is no appreciable Mn mixed valence, and that the MnO{sub 6} octahedra are well ordered. This further supports the proposed mechanism for CMR in Tl{sub 2}Mn{sub 2}O{sub 7} based on our earlier structural studies. {copyright} {ital 1997} {ital The American Physical Society}

• Research Organization: Lawrence Livermore National Laboratory
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 439048
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 2 Vol. 55; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION SPECTRA
CRYSTAL STRUCTURE
ELECTRONIC STRUCTURE
MAGNETORESISTANCE
MANGANESE COMPOUNDS
MANGANESE OXIDES
OXYGEN COMPOUNDS
PYROCHLORE
STRUCTURAL MODELS
THALLIUM COMPOUNDS
THALLIUM OXIDES
X-RAY SPECTRA