Synthesis, Crystal Chemistry, and Electrical and Magnetic Properties of Sr
Sr{sub 3}Fe{sub 2-x}Co{sub x}O{sub 7-{delta}} oxides crystallizing in a tetragonal perovskite-related intergrowth structure have been synthesized for 0{<=}x{le}0.8 and characterized by X-ray powder diffraction, wet-chemical analysis, and electrical and magnetic measurements. The lattice parameters, oxygen content, and average oxidation state of iron and cobalt decrease with increasing Co content x. However, the samples show instability on exposure to ambient air for prolonged periods of time due to a possible reaction with H{sub 2}O and CO{sub 2}. Resistivity measurements indicate that the samples exhibit a semiconducting behavior at low temperatures (80{<=}T{le}680 K) and the resistivity value decreases with increasing Co content. For T > 680 K, the resistivity versus temperature plots exhibit a change in the sign of the slope from negative to positive due to oxygen loss at higher temperatures. Low-temperature resistivity data show an exponential temperature dependence of {rho}{proportional_to}exp(T{sub 0}/T){sup {nu}} with {nu}=1/2 for samples with 0{<=}x{le}0.25 and {nu}=1/4 for samples with 0.6{<=}x{le}0.8 suggesting a transition from activated carriers involving a coulomb gap to thermally activated hopping as the Co content increases. SQUID magnetometer measurements indicate a transition from antiferromagnetic behavior to weak ferromagnetic behavior as the Co content increases.
- Research Organization:
- Texas Materials Institute, The University of Texas at Austin, Austin, TX (US)
- Sponsoring Organization:
- Welch Foundation; CONICET (Argentina) (US)
- OSTI ID:
- 784447
- Journal Information:
- Journal of Solid State Chemistry, Vol. 158, Issue 2; Other Information: PBD: 1 May 2001; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHEMISTRY
LATTICE PARAMETERS
MAGNETIC PROPERTIES
SYNTHESIS
TEMPERATURE DEPENDENCE
STRONTIUM OXIDES
IRON OXIDES
COPPER OXIDES
CRYSTAL-PHASE TRANSFORMATIONS
CHEMICAL PREPARATION
X-RAY DIFFRACTION
CHEMICAL ANALYSIS
VALENCE
IRON
COBALT
ELECTRIC CONDUCTIVITY
SEMICONDUCTOR MATERIALS
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
ANTIFERROMAGNETISM
FERROMAGNETISM
CRYSTAL-PHASE TRANSFORMATION
EXPERIMENTAL DATA