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Author Jhans, H. ♦ Kim, D. ♦ Rasmussen, R. J. ♦ Honig, J. M.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ LANTHANUM OXIDES ♦ ELECTRIC CONDUCTIVITY ♦ NICKEL OXIDES ♦ HZ RANGE ♦ KHZ RANGE ♦ MHZ RANGE 01-100 ♦ TEMPERATURE RANGE 0065-0273 K ♦ SCALING ♦ TERNARY COMPOUNDS
Abstract We have carried out ac-conductivity {sigma}({omega}) measurements on La{sub 2}NiO{sub 4+{delta}},0{lt}{delta}{le}0.08, in the frequency ({omega}) and temperature ranges 5-13 MHz and 75-300 K. The ac conductivity follows a set of basic characteristics: (i) {sigma}({omega}) obeys the {omega}{sup s} power law (s{approximately}0.38-0.85). (ii) At higher frequencies, {sigma}({omega}) saturates. To our knowledge, saturation of {sigma}({omega}) with {omega} in the radio frequency range has not been previously reported for an electronic system. (iii) {sigma}({omega}) is weakly temperature dependent in the dispersive region. (iv) Below the saturation region, for a fixed {delta}, the reduced conductivity {sigma}({omega})/{sigma}(0), at various values of T can be scaled to a generalized reduced frequency {omega}{sub {ital n}}={omega}/{sigma}(0)T{sup n}. For {delta}=0.01-0.08, n ={minus}1/3 or {minus}1/4. (v) Furthermore, at a fixed T, the reduced conductivities for various {delta} lie on a universal curve; n in this case varies from {minus}1/4 to {minus}1/2. (vi) Good agreement of data with the Summerfield extended pair approximation theory, {sigma}({omega})/{sigma}(0)=1+{bold (}{ital A}{omega}{alpha}{ital e}{sup 2}/ {sigma}(0){ital k}{sub {ital BT}}{sup {ital n}}{bold )}{sup {ital b}}, is found; {ital b}{approximately}0.64{endash}1. (vii) Our data analysis reveals two loss peaks; the first is located near the critical frequency {omega}{sub {ital c}} below which the imaginary part of conductivity {sigma}{sub 2}({omega}) is proportional to {omega}. (viii) The relation {sigma}(0){proportional_to}{omega}{sub {ital c}} is obeyed, with {omega}{sub {ital c}}{proportional_to}exp[{minus}({ital T}{sub 2}/{ital T}){sup 1/3}]. The second loss peak lies near the onset of saturation. These characteristic signatures in the ac conductivity point to a transport mechanism involving localized states near the Fermi level. {copyright} {ital 1996 The American Physical Society.}
ISSN 01631829
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-10-01
Publisher Department Purdue Research Foundation
Publisher Place United States
Journal Physical Review, B: Condensed Matter
Volume Number 54
Issue Number 16
Organization Purdue Research Foundation


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