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Magnetic and Mössbauer Studies of the System LaCo 1− x Zr x O 3 ( x = 0.1, 0.3, 0.5)
Author(s) -
Johri U. C.,
Singru R. M.,
Bahadur D.
Publication year - 1990
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221610136
Subject(s) - ion , crystallography , mössbauer spectroscopy , atmospheric temperature range , magnetic susceptibility , chemistry , mössbauer effect , analytical chemistry (journal) , materials science , physics , organic chemistry , chromatography , meteorology
Abstract Mössbauer studies on well‐characterized LaCo 1− x Zr x O 3 ( x = 0.1, 0.3, 0.5) are carried out in the 80 to 700 K temperature range and they show that cobalt ions exist predominantly in the low spin Co III (t 2g 6 e g 0 ) and Co II (t 2g 6 e g 1 ) states at 80 K which transform partially to high‐spin Co 3+ (t 2g 4 e g 2 ) ions upto ≈ 500 K. In the 80 to 700 K region the system LaCo 0.9 Zr 0.1 O 3 behaves almost similar to LaCoO 3 . However, above 500 K, in the system LaCo 1− x Zr x O 3 ( x = 0.3, 0.5) Co 3+ ions capture an electron from Co II and transform into Co 2+ (t 2g 5 e g 2 ) and Co III ions pairs. The magnetic susceptibility data recorded are consistent with the present Mössbauer resülts. The inverse magnetic susceptibility versus temperature curves for the systems LaCo 1− x Zr x O 3 ( x = 0.3, 0.5) show different slopes in the 300 to 800 K temperature range. The higher slopes above ≈ 500 and ≈ 550 K for the system LaCo 0.7 Zr 0.3 O 3 and LaCo 0.5 Zr 0.5 O 3 , respectively, indicate lower μ eff which, in turn, suggests the generation of Co 2+ ions at the cost of Co 3+ ions. The generation of low spin Co II and Co III at low temperatures is attributed to larger crystal field splitting Δ cf compared to exchange energy Δ ex in the system as a result of tetravalent Zr ion substitution.