The heterogeneous metal oxide composite (1x)La2O3xSrOCo3O4 (where x0.8), comprised primarily of the three oxide phases (La2O3, spinel Co3O4, and SrO), exhibits a special temperature-magnetic response profile. The coercivity of the composite decreases with increasing temperature from 70to200K, but increases from 200to298K. This outcome is upheld because of the occurrence of three structures, which are the perovskite La1αSrαCoO3β(αx) phase that is formed at the interface region of the above three oxides, the presence of La3+ in the Co3O4 phase, and the interface between SrO and Co3O4 phases (domains). The first two structures are deemed responsible for manifestation of ferromagnetism at low temperature, while the last one for room temperature ferromagnetism. We also noted that the third structure could reveal noticeable magnetic properties only when the three major oxide phases are mixed in nanometer scale as the magnetic behavior is triggered through the deformation of octahedral Co-O cells located at the surface of the spinel domains. To realize such an ultrahigh dispersion of the three oxide phases, pyrolysis of the metal-ion-containing hydrogel made of the three metal ions (La3+, Sr2+, and Co2+) and organic moieties (e.g., citric acid and glycine) is an effective approach. In contrast to the homogeneous perovskite solid solution La1xSrxCoO3δ(x0.5), the present type of composite shows stronger coercivity but weaker remanence induction at temperatures below 200K. Other than the temperature effect, the influence of the organic components in the metal-ion-containing hydrogel on the interface-sustained magnetism has also been studied.

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