Room temperature relaxor ferroelectricity and spin glass behavior in Sr2FeTiO6 double perovskite
Room temperature relaxor ferroelectricity and spin glass behavior in Sr2FeTiO6 double perovskite
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DOI：
10.1016/j.jallcom.2012.01.091
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发表时间：
2012-05
影响因子：
6.2
通讯作者：
P. N. Lekshmi;S. S. Pillai-S.;K. Suresh;P. Santhosh;M. Varma
中科院分区：
文献类型：
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作者：
P. N. Lekshmi;S. S. Pillai-S.;K. Suresh;P. Santhosh;M. Varma
研究了复合Sr2FeTiO6双钙钛矿的结构、介电和磁性能。 X 射线粉末衍射图的 Reitveld 分析表明，该材料稳定在具有 Pm3´m 空间群的立方钙钛矿相中，而没有 B 位阳离子排序。晶体结构研究的温度演变表明结构不随温度变化。扫描电镜照片显示晶粒分布不均匀，平均晶粒尺寸为1-7.5μm。键价和计算和扩散辅助小极化子跳跃传导机制证实了Fe/Ti离子的混合价态。介电谱显示出广泛的介电异常，并且介电最大值随频率向更高温度移动，表现出典型的弛豫铁电行为。基于唯象参数（Tm、TB、γ、ΔTrelax）对弛豫行为进行了定量表征。介电弛豫与非线性 Vogel Fulcher 关系的一致性表明该系统确实是表现出玻璃特性的弛豫剂。输运研究显示出类似半导体的行为和可忽略不计的磁阻。此外，磁性特征在 16K 以下表现出非金属类自旋玻璃态，这是由反铁磁态和铁磁态之间的竞争相互作用驱动的。
The structure, dielectric and magnetic properties of complex Sr2FeTiO6double perovskite have been investigated. Reitveld analysis of X-ray powder diffraction pattern reveals that the material is stabilized in a cubic perovskite phase with Pm3¯m space group without the B-site cations ordering. The temperature evolution of crystal structural studies indicates the absence of structural changes with temperature. The scanning electron micrograph exhibits heterogeneous grain distribution with average grain size of 1–7.5μm. The bond valence sum calculations and diffusion-assisted small-polaron hopping conduction mechanism confirm the mixed valence state of Fe/Ti ions. Dielectric spectra show a broad dielectric anomaly coupled with a shift in dielectric maxima towards higher temperature with frequency, exhibiting a typical relaxor ferroelectric behavior. The relaxor behavior has been quantitatively characterized based on the phenomenological parameters (Tm, TB, γ, ΔTrelax). The agreement of dielectric relaxation with non-linear Vogel Fulcher relation indicates that the system is indeed a relaxor exhibiting glassy characteristics. The transport studies show a semiconductor like behavior and a negligible magnetoresistance. Furthermore, the magnetic characterisation exhibits a non-metallic spin-glass-like state below 16K, driven by competing interactions between the antiferromagnetic and the ferromagnetic states.