Tuning of magnetic and electronic states by control of oxygen content in lanthanum strontium cobaltites

Journal Article · Thu Jun 01 00:00:00 EDT 2006 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.73.2· OSTI ID:20788208

Kolesnik, S; Dabrowski, B; Mais, J; Majjiga, M; Chmaissem, O; Baszczuk, A; Jorgensen, J D ^[1]

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1. Department of Physics, Northern Illinois University, DeKalb, Illinois 60115 (United States)

We report on the magnetic, resistive, and structural studies of perovskite La{sub 1/3}Sr{sub 2/3}CoO{sub 3-{delta}}. By using the relation of synthesis temperature and oxygen partial pressure to oxygen stoichiometry obtained from thermogravimetric analysis, we have synthesized a series of samples with precisely controlled {delta}=0.00-0.49. These samples show three structural phases at {delta}=0.00-0.15, {approx_equal}0.25, {approx_equal}0.5, and two-phase behavior for other oxygen contents. The stoichiometric material with {delta}=0.00 is a cubic ferromagnetic metal with the Curie temperature T{sub C}=274 K. The increase of {delta} to 0.15 is followed by a linear decrease of T{sub C} to {approx_equal}160 K and a metal-insulator transition near the boundary of the cubic structure range. A further increase of {delta} results in the formation of a tetragonal 2a{sub p}x2a{sub p}x4a{sub p} phase for {delta}{approx_equal}0.25 and a brownmillerite phase for {delta}{approx_equal}0.5. At low temperatures, these are weak ferromagnetic insulators (canted antiferromagnets) with magnetic transitions at T{sub m}{approx_equal}230 and 120 K, respectively. At higher temperatures, the 2a{sub p}x2a{sub p}x4a{sub p} phase is G-type antiferromagnetic between 230 K and {approx_equal}360 K. Low temperature magnetic properties of this system for {delta}<1/3 can be described in terms of a mixture of Co{sup 3+} ions in the low-spin state and Co{sup 4+} ions in the intermediate-spin state and a possible spin transition of Co{sup 3+} to the intermediate-spin state above T{sub C}. For {delta}>1/3, there appears to be a combination of Co{sup 2+} and Co{sup 3+} ions, both in the high-spin state with dominating antiferromagnetic interactions.

• OSTI ID: 20788208
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 73, Issue 21; Other Information: DOI: 10.1103/PhysRevB.73.214440; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANTIFERROMAGNETIC MATERIALS
ANTIFERROMAGNETISM
COBALT IONS
COBALT OXIDES
CRYSTAL STRUCTURE
CURIE POINT
ELECTRONS
EXCHANGE INTERACTIONS
FERROMAGNETIC MATERIALS
HIGH SPIN STATES
LANTHANUM COMPOUNDS
MAGNETIC PROPERTIES
OXYGEN
PARTIAL PRESSURE
PEROVSKITE
SPIN
STRONTIUM COMPOUNDS
TEMPERATURE DEPENDENCE
THERMAL GRAVIMETRIC ANALYSIS