Department of Physics, V. N. Autonomous College, Jajpur Road, Jajpur 755019, Orissa, India.
J Phys Condens Matter. 2010 Jan 20;22(2):025901. doi: 10.1088/0953-8984/22/2/025901. Epub 2009 Dec 9.
A Pb(Fe(½)Nb(½))O(3) ceramic sample was prepared through a high temperature solid-state reaction technique. The formation of a single-phase perovskite compound was confirmed by an x-ray diffraction technique. Dielectric and impedance parameters were measured as a function of frequency (10(2)-10(6) Hz) at different temperatures (28-200 °C). The results were described using an equivalent circuit model and by extending the universal capacitor concept introduced by Jonscher. Bulk permittivity of the material and the power law exponent (extracted from impedance data) exhibits an anomaly at a particular temperature related to the ferroelectric-paraelectric transition. A slow relaxation process has been observed in the vicinity of the transition temperature. Temperature dependent magnetization (2-300 K) was measured at different magnetic fields in both zero-field-cooled (ZFC) and field-cooled (FC) modes. An antiferromagnetic transition was observed at 158 K but an unusual increase in magnetization below this transition indicates the onset of weak ferromagnetism at low temperature in this system. Nonlinear M-H and a finite opening in the hysteresis loop at 2 K substantiate the presence of ferromagnetic interactions. Significantly, a thermomagnetic history-dependent feature is observed below 9 K. The ZFC magnetization shows a sharp fall and it bifurcates from the monotonically increasing FC counterpart on decreasing temperature. This temperature, where ZFC magnetization shows a sharp peak, decreases with the increase in measurement field and it indicates the presence of a metastable magnetic state at low temperature.
采用高温固相反应技术制备了 Pb(Fe(½)Nb(½))O(3)陶瓷样品。通过 X 射线衍射技术证实了单相钙钛矿化合物的形成。介电常数和阻抗参数作为频率（10(2)-10(6) Hz）的函数，在不同温度（28-200 °C）下进行了测量。结果使用等效电路模型进行了描述，并通过扩展 Jonscher 引入的通用电容器概念进行了扩展。材料的体介电常数和幂律指数（从阻抗数据中提取）在与铁电-顺电相变相关的特定温度下表现出异常。在相变温度附近观察到了缓慢的弛豫过程。在不同磁场下测量了 2-300 K 温度下的磁化（ZFC 和 FC 模式）。在 158 K 处观察到反铁磁转变，但在此转变下方磁化的异常增加表明在该系统中低温下弱铁磁性的出现。非线性 M-H 和在 2 K 下滞后回线的有限开口证实了铁磁相互作用的存在。重要的是，在 9 K 以下观察到与热磁历史相关的特征。ZFC 磁化急剧下降，并在温度降低时从单调增加的 FC 对应物分叉。ZFC 磁化显示出尖锐峰值的温度随测量场的增加而降低，这表明低温下存在亚稳磁态。
