NMR Evidence for the 8.5 K Phase Transition in Americium Dioxide
NMR Evidence for the 8.5 K Phase Transition in Americium Dioxide
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二氧化镅中 8.5 K 相变的 NMR 证据
DOI：
10.1143/jpsj.79.053705
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
H. Chudo
中科院分区：
文献类型：
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作者：
Y. Tokunaga;T. Nishi;S. Kambe;M. Nakada;A. Itoh;Y. Homma;H. Sakai;H. Chudo
我们在这里报告的第一个NMR研究氧化镅（AmO 2）。30多年前，根据磁化率数据，该化合物在8.5 K时发生了相变，但没有从显微镜测量中获得证据。制备了含90原子的~（243）AmO_2粉末样品。%~（17）O，并在1.5 ~ 200 K温度范围内进行了~（17）O NMR。在低于8.5K的温度下，~（17）ONMR信号强度突然下降，在1.5K时，我们观察到了一个极宽的谱线，其谱线在外加磁场下可达~（14）kOe。这些数据提供了第一个微观证据的相变在这个系统中作为一个整体属性。此外，17 O核磁共振谱已被发现分裂成两个峰的顺磁状态，这种效果还没有报道的锕系二氧化物研究到现在。我们认为这种分裂是由243 Am α衰变的自辐射损伤引起的。
We report here the first NMR study of americium dioxide (AmO2). More than 30 years ago, a phase transition was suggested to occur in this compound at 8.5 K based on magnetic susceptibility data, while no evidence had been obtained from microscopic measurements. We have prepared a powder sample of243AmO2containing 90 at. %17O and have performed17O NMR at temperatures ranging from 1.5 to 200 K. After a sudden drop of the17O NMR signal intensity below 8.5 K, at 1.5 K we have observed an extremely broad spectrum covering a range of ∼14 kOe in applied field. These data provide the first microscopic evidence for a phase transition as a bulk property in this system. In addition, the17O NMR spectrum has been found to split into two peaks in the paramagnetic state, an effect which has not been reported for actinide dioxides studied up to now. We suggest that the splitting is induced by self-radiation damage from the alpha decay of243Am.