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J. Korean Ceram. Soc. > Volume 28(8); 1991 > Article
Journal of the Korean Ceramic Society 1991;28(8): 603.
산소 1기압하에서 합성된 산소결함 Perovskite(CaLa)(MgMn)O$_{5.43}$의 물리화학적 특성연구
최진호, 홍승태1, 김승준1
서울대학교 자연대 화학과
1분자과학연구소 무기재료부
Oxygen-Deficient Perovskite, (CaLa) (MgMn)O5.43 Prepared Under Oxygen Gas Pressure of 1 Bar
An oxygen deficient perovskite (CaLa)(MgMn)O5.43, with the cubic unit cell parameter of 3.826$AA$, was prepared 115$0^{circ}C$ for 10 hrs under the ambient oxygen gas pressure. The average oxidation state of manganese was determined to be 3.86 by the iodometric titration, so that the perovskite could be formulated as (CaLa) ({{{{ { MgMn}`_{ chi } ^{II } }}{{{{ { Mn}`_{ y} ^{III } }}{{{{ { Mn}`_{1- chi -y } ^{IV } }})O5.43 (2x+y=0.14). From X-ray photoelectron spectroscopy, the manganese ions in the lattice are mostly tetravalent, but two paramagnetic configurations were observed in the EPR spectrum: One sharp isotropic signal with hyperfines (ΔH 50 G, g=1.997$pm$0.002 and │A│=82(4)$times$10-4 cm-1) and a broad isotropic one (ΔH 1600 G, g=1.994$pm$0.002), those which correspond respectively to Mn(II) and Mn(IV) ions. According to the magnetic susceptibility measurement, it follows the Curie-Weiss law from 20 K up to room temperature with $mu$eff=5.23 $mu$B, which is relatively larger than spin-only value({{{{ { mu }`_{eff} ^{s.o } }}=4.04 $mu$B) due to the effect of weak ferromagnetic coupling. Such a result is in accord with a theory of semicovalence exchange.
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