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Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-Ku, Tokyo, 153-8505, Japan
| Colossal magnetoresistance (CMR) properties of La(Mn1-xNix)O3+δ (0≤x≤0.1) are investigated. The partial replacement of Mn3+ by Ni2+ causes the conversion of Mn3+ to Mn4+. However, the CMR effect of the manganites with excess oxygen decreases as the Ni amount is increased. The samples were prepared both in air and in oxygen atmosphere in order to change the Mn4+ ratio and the concentration of Mn4+ was determined quantitatively. We measured the temperature dependence of magnetization after cooling the sample in zero field (ZFC) or in the field (FC). According to the temperature dependence of coercive field and thermoremanent magnetization, a cluster glass like transition is presumed. We propose that the frustration of the interaction among ferromagnetic clusters introduced by substituting Ni for Mn causes the decrease and increase of the magnetoresistance. |
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