High-Pressure Mössbauer Measurements on Nanocrystalline Perovskite (La,Sr)(Mn,Fe)O3
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- 作者：Usha Chandra ; Prerana Mudgal ; Manoj Kumar ; Rajeev Rawat ; G. Parthasarathy ; Nita Dilawar and A. K. Bandyopadhyay
- 关键词：high ; pressure electrical resistivity ; high ; pressure Mö ; ssbauer spectroscopy ; manganite ; nanocrystalline ; perovskite
- 刊名：Hyperfine Interactions
- 出版时间：June 2005
- 出版年：2005
- 期刊代码：18_03043843
- 类别：cp
- 卷：163
- 期：1-4
- 页码：129-141
- 数据来源：sp
摘要
We report here the Mössbauer measurements on nanocrystalline perovskite structured manganite La0.8Sr0.2Mn0.8Fe0.19 57Fe0.01O3 as a function of pressure up to 10 GPa at room temperature. The nanocrystalline sample, prepared by sol–gel technique found to have crystallite sizes of ∼138 ± 10 Å. Zero-field electrical resistivity measurements with temperature support the nanocrystalline nature. At ambient pressure, Fe3+ as well as Fe4+ ions are distributed in two different environments – Fe3+ in low symmetric site surrounded by Mn3+ ions only while Fe4+ in high symmetric site with at least one Mn3+ ion. Pressure seems to affect the higher symmetric site. A sudden increase in isomer shift at 0.52 GPa indicates the first order phase transition representing the transformation of Fe4+ to Fe3+. Another transition at 3.7 GPa, represents the presence of Fe3+ in single kind of environment. Pressure dependence of electrical resistivity measurements verifies the transitions attributing the first order transition to the cross over of localized-electron to band magnetism.