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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 16, Number 2
BKCSDE 16(2)
February 20, 1995 

Pressure Dependence of the Oxidation State of Manganese and Magnetic Property of CaLaMgMnO6-x
Jin-Ho Choy*, Seung-Tae Hong, Nam-Gyu Park, Song-Ho Byeon, Gerard Demazeau
Oxygen deficient perovskites CaLaMgMnO6-x were prepared in three different oxygen pressures; at 1150 ℃ under oxygen gas pressure of 0.1 MPa (L), at 950 ℃ under 0.1 GPa (M), and at 900 ℃ under high pressure of 6 GPa (H). From iodometric titration and EPR spectra, the samples could be formulated as (CaLa)(MgMnⅡxMnⅢyMnⅣ 1-x-y)O5.43(2x-y=0.14) (L), CaLaMgMnⅢ0.1MnⅣ 0.9O5.45(M) and CaLaMgMnⅣ0.93MnⅥ 0.07O5.57(H), and it could be confirmed that Mn(Ⅳ ) ions are the most stable in an octahedral site of perovskites, but a small content of Mn(Ⅱ), Mn(Ⅲ) or Mn(Ⅳ) ions are also stabilized in an oxygen-vacant site due to the site preferences of such ions, depending on the oxygen pressure. The anomalous magnetic properties of Land M might result from the simultaneous occurrence of antiferromagnetism and ferromagnetism below TC or TN, which could be explained by semicovalence magnetic exchange model.
105 - 110
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