Suspicious electron-doped CMR in sintered La1-xCexMnO3
  La0.7Ce0.3MnO3 (LCeMO) is known usually called an electron doped colossal magnetotesistance material, which contains multiphase of n-type LCeMO, CeO2 and Mn-O. However, the present energy dispersion spectroscopy measurement shows that the La0.85Ce0.017MnO3+delta is the main phase in the bulk solid of material, which does not have the LCeMO phase. This finding is consistent with the XRD data analysis which indicates that the composition is La0.87Ce0.014MnO2.93. Since the highly localized f electrons of Ce ions may not be transferred to Mn ions significant oxygen deficiency is needed to drive La0.87Ce0.014MnO2.93 into n-type state that, which conflicts with the observation of a low TC fact of the vacuum annealed sample and to the natural tendency for the absorption of excess oxygen that yields a positive delta. Similar properties are also found in La1-xTexMnO3+delta, La1-xSnxMnO3+delta and La1-xZrxMnO3+delta systems. The present study casts doubt on the interpretation of n-ype electronic property in bulk solid of LCeMO and proposed that the n-type CMR may be formed in metastable state. 
Hsiung Chou, C. B. Wu and S. G. Hsu