Crystal structure, magnetic and transport properties, and electronic band structure of A{sub 2}Mn{sub 2}O{sub 7} pyrochlores (A=Y,thinspIn,thinspLu, and Tl)

Journal Article · Fri Jan 01 04:00:00 EST 1999 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.59.1249· OSTI ID:289177

Shimakawa, Y; Kubo, Y ^[1]; Hamada, N ^[2]; Jorgensen, J D; Hu, Z; Short, S ^[3]; Nohara, M; Takagi, H ^[4]

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1. Fundamental Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba 305-8501 (Japan)
2. Department of Physics, Faculty of Science and Technology, Science University of Tokyo, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)
3. Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
4. Institute for Solid State Physics, University of Tokyo, 7-22-1, Roppongi, Minato-ku, Tokyo 106-6888 (Japan)

Crystal structures, magnetic and transport properties, and electronic band structures for four compounds with the pyrochlore structure, Tl{sub 2}Mn{sub 2}O{sub 7}, which exhibits colossal magnetoresistive behavior, and insulating A{sub 2}Mn{sub 2}O{sub 7} (A=Y,thinspIn and Lu), are discussed. The cubic unit cell dimensions increase with increasing ionic size of the A{sup 3+} ions. The ferromagnetic behavior is consistent with a superexchange interaction of Mn{sup 4+} spins with an intermediate Mn-O-Mn bond angle of about 130{degree}. In In{sub 2}Mn{sub 2}O{sub 7} and Tl{sub 2}Mn{sub 2}O{sub 7}, strong hybridization of the In(5s)/Tl(6s) orbital with O(2p) and Mn(3d) may enhance the ferromagnetic interaction, leading to high transition temperatures over 120 K. The metallic behavior of Tl{sub 2}Mn{sub 2}O{sub 7} also originates from the hybridization among Tl(6s), O(2p), and Mn(3d). The free-electron-like minority down-spin band crosses the Fermi energy, leading to spin-polarized conduction. At the ferromagnetic Curie temperature, where majority local spins align, spin-polarized conduction electrons are produced: Thus, a ferromagnetic-and-metallic state appears in the Tl{sub 2}Mn{sub 2}O{sub 7} pyrochlore. {copyright} {ital 1999} {ital The American Physical Society}

• OSTI ID: 289177
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 2 Vol. 59; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BAND THEORY
CRYSTAL STRUCTURE
CURIE POINT
ELECTRONIC STRUCTURE
EXCHANGE INTERACTIONS
FERROMAGNETIC MATERIALS
HYBRIDIZATION
INDIUM COMPOUNDS
INDIUM OXIDES
LUTETIUM COMPOUNDS
LUTETIUM OXIDES
MAGNETIC PROPERTIES
MAGNETIZATION
MANGANESE OXIDES
POLARIZATION
PYROCHLORE
SPECIFIC HEAT
SPIN EXCHANGE
THALLIUM COMPOUNDS
THALLIUM OXIDES
YTTRIUM COMPOUNDS