Infrared reflectivity of single-crystal Bi sub 2 M m +1 Co sub m O sub y ( M =Ca,Sr,Ba; m =1,2), Bi sub 2 Sr sub 3 Fe sub 2 O sub 9. 2 , and

Journal Article · Fri Feb 01 00:00:00 EST 1991 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.43.3026· OSTI ID:5844968

Watanabe, Y; Tsui, D C ^[1]; Birmingham, J T; Ong, N P ^[2]; Tarascon, J M ^[3]

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1. Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (USA)
2. Department of Physics, Princeton University, Princeton, New Jersey 08544 (USA)
3. Bell Communications Research, Red Bank, New Jersey 07701 (USA)

The infrared reflectivity of single crystals of Bi{sub 2}{ital M{ital m}+1}Co{sub {ital m}}O{sub {ital y}} ({ital M}=Ca, Sr, Ba; {ital m}=1,2), Bi{sub 2}Sr{sub 3}Fe{sub 2}O{sub 9.2}, and Bi{sub 2}Sr{sub 2}MnO{sub 6.25} was measured at room temperature between 0.08 and 1.4 eV. A broad absorption band is observed in the mid-ir range (near 0.5 eV) in all the compounds studied, and an absorption band near 0.3 eV is observed in the insulating system. In terms of a conventional Drude-Lorentz model, the measured reflectivity and the frequency-dependent conductivity between 0.2 and 1 eV can be fitted with three broad Lorentzians and a Drude term. For the Bi{sub 2}{ital M{ital m}+1}Co{sub {ital m}}O{sub {ital y}} system, the reflectivity increases and assumes a more metallic profile as the number of Co-O layers per unit cell increases, or as the ionic radius of {ital M} increases. The apparent plasma edge of this system is about 0.3 eV, and remains unshifted for all Bi{sub 2}{ital M3}Co{sub 2}O{sub {ital y}}, as observed in the high-{ital T}{sub {ital c}} cuprates in which the carrier density is changed by doping. In addition, as observed in the high-{ital T}{sub {ital c}} cuprates, the reflectivity-frequency profile below the apparent plasma edge is less curved than predicted by the Drude model. For the Bi{sub 2}{ital M{ital m}+1}Co{sub {ital m}}O{sub {ital y}} system, the intensity of the mid-ir absorption approximately scales with that of the free-carrierlike absorption.

• OSTI ID: 5844968
• Journal Information: Physical Review, B: Condensed Matter; (USA), Vol. 43:4; ISSN 0163-1829
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE
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360204* - Ceramics
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