Structural and electronic properties of the perovskite-type ferrimagnetic semiconductor CaCo0.5Zr0.5O3

The purpose of this work is to report the structural, magnetic, electrical and electronic properties of the perovskite-type semiconductor CaCo0.5Zr0.5O3. For the synthesis of the material, the standard solid-state reaction method was employed, followed by an analysis of its crystal structure by Rietveld refinement applied to X-ray diffraction patterns, which revealed the crystallisation of the compound in an orthorhombic structure belonging to the Pcmn space group. Through morphological and compositional analyses, it was determined that the surface of the samples evidenced mean grain size of 1.47 ± 0.01 µm, as well as the occurrence of minimal levels of impurities. The curves of magnetic susceptibility as a function of temperature and magnetisation as a function of external magnetic field showed a weakly ferrimagnetic response of the material, with Weiss temperature =-72 K and effective magnetic moment 1.78 B, suggesting that Co4+ does not present crystalline field splitting and the spins adopt low spin states. The electrical resistivity exhibits behaviour and order of magnitude (106 .m) characteristic of a semiconductor feature and current-voltage curves with a typical thermistor-type semiconductor response. Density of states and band structure analysis indicate that the material exhibits ferromagnetic semiconductor-like behaviour at low temperatures, with a mean band gap of 0.89 eV and an effective magnetic moment of 2.0 µB.

本研究旨在报道钙钛矿型半导体CaCo0.5Zr0.5O3的结构、磁学、电学及电子学特性。本研究采用标准固相反应法合成该材料，随后通过对X射线衍射图谱进行Rietveld精修（Rietveld refinement）分析其晶体结构，结果表明该化合物结晶为正交晶系结构，所属空间群为Pcmn。通过形貌与成分分析，确定样品表面的平均晶粒尺寸为1.47 ± 0.01 μm，且仅存在极微量杂质。磁化率随温度变化曲线与磁化强度随外磁场变化曲线显示，该材料呈现弱铁磁响应，其韦斯温度（Weiss temperature）θ=-72 K，有效磁矩为1.78 μB，表明Co⁴+不存在晶体场分裂，自旋处于低自旋态。电阻率的变化行为与数量级（~10⁶ Ω·m）符合半导体特性，电流-电压曲线则呈现典型的热敏电阻型半导体响应。态密度（Density of states）与能带结构分析表明，该材料在低温下表现出类铁磁半导体特性，平均能带隙为0.89 eV，有效磁矩为2.0 μB。