Spin gap formation in the heavy fermion skutterudite compound CeRu4Sb12
Spin gap formation in the heavy fermion skutterudite compound CeRu4Sb12
复制标题
重费米子方钴矿化合物 CeRu4Sb12 中自旋间隙的形成
DOI：
10.1103/physrevb.68.094425
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发表时间：
2003
影响因子：
3.7
通讯作者：
J. So
中科院分区：
文献类型：
--
作者：
D. Adroja;J;K. Mcewen;N. Takeda;M. Ishikawa;J. So
CeRu4Sb12是一种混合价态近道晶格体系，其电荷激发谱开隙为47 meV。为了研究自旋激发谱对温度、能量和动量的依赖关系，我们在5 ~ 250 K的宽温度范围内进行了入射中子能量为100 meV的非弹性中子散射测量。我们在5和60 K下测量的结果表明，在磁谱中打开了一个类似于30 meV的自旋间隙，并且在此之上，非弹性磁响应形成了一个连续体，直到95 meV。令人惊讶的是，自旋间隙在我们的分辨率范围内既没有波矢量Q依赖，也没有从5到100 K的温度依赖。另一方面，在100k以上，自旋间隙开始填满，在更高的温度下，磁响应变成纯粹的准弹性。在100 K以上观察到的剧烈变化可能与ce4f电子的相干温度有关，而观察到的自旋间隙的Q独立性表明单离子近藤相互作用在间隙形成机制中很重要。我们用理论模型来讨论我们的结果。
CeRu4Sb12 is a mixed-valence Kondo-lattice system with a gap of 47 meV opening in the charge excitation spectrum, measured by the infrared spectroscopy technique. In order to study the temperature and energy and momentum dependence of the spin excitation spectrum, we have made inelastic neutron scattering measurements over a wide range of temperature between 5 and 250 K with an incident neutron energy of 100 meV. Our results measured at 5 and 60 K show that a spin gap of similar to30 meV opens in the magnetic spectrum and above it the inelastic magnetic response forms a continuum right up to 95 meV. Surprisingly, the spin gap shows neither wave vector Q dependence within our resolution nor temperature dependence from 5 to 100 K. On the other hand, the spin gap starts to fill up above 100 K and the magnetic response becomes purely quasielastic at higher temperatures. The dramatic change observed above 100 K can be related to the coherence temperature of the Ce 4f electrons while the observed Q independence of the spin gap implies that single-ion Kondo interactions are important in the gap formation mechanism. We discuss our results in terms of theoretical models.