Abstract

Experimental data on the properties of ceramic manganites La_0.7Sr_0.3Mn_0.9\(\left( {{\text{Zn}}_{{{\text{0}}{\text{.5}}}}^{{{\text{2 + }}}}{\text{Ti}}_{{{\text{0}}{\text{.5}}}}^{{{\text{4 + }}}}} \right)\)_0.1O_{3 + γ} with different oxygen concentrations are presented. Variations of oxygen nonstoichiometry index (γ) were achieved by heat treatment of the samples at different partial pressure of oxygen in the gas phase. All synthesized samples have rhombohedral structure. The γ index is calculated from the data on the change in unit cell volume of manganites relative to stoichiometric sample. Unit cell volume decreases as a function of γ in the range from –0.008 to 0.009, and specific magnetization exhibits the tendency for increase. Curie point is weakly dependent on γ, while the sample with the maximum oxygen content has the smallest temperature interval width of magnetic transition. The temperature of “metal–semiconductor” phase transformation decreases with increasing γ. Manganite with γ = –0.008 has the highest absolute value of magnetoresistance: |MR| = 60% in the field of 0.92 T. Established regularities are discussed taking into account mechanisms of charge compensation, electronic configuration and radii of manganese substituents, double exchange, Coulomb interaction, diffusion processes and the formation of microinhomogeneities.

中文翻译：

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氧浓度对锌钛复合锰置换La-Sr锰酸盐结构和电磁特性的影响

摘要

陶瓷锰酸盐特性实验数据 La _0.7 Sr _0.3 Mn _0.9 \(\left( {{\text{Zn}}_{{{\text{0}}{\text{.5}}}}^{{ {\text{2 + }}}}{\text{Ti}}_{{{\text{0}}{\text{.5}}}}^{{{\text{4 + }}}} } \right)\) _0.1 O _{3 + γ}给出了不同的氧气浓度。通过在气相中不同的氧分压下对样品进行热处理来实现氧非化学计量指数 (γ) 的变化。所有合成样品均具有菱面体结构。γ 指数是根据锰酸盐晶胞体积相对于化学计量样品的变化数据计算得出的。晶胞体积作为 γ 的函数在 –0.008 到 0.009 的范围内减小，并且比磁化强度呈现增加的趋势。居里点对γ的依赖性较弱，而氧含量最大的样品具有最小的磁跃迁温度区间宽度。“金属-半导体”相变的温度随着 γ 的增加而降低。γ = –0.008 的锰矿具有最高的磁阻绝对值： |先生| = 0.92 T 领域中的 60%。讨论了已建立的规律，考虑了电荷补偿机制、锰取代基的电子配置和半径、双交换、库仑相互作用、扩散过程和微不均匀性的形成。