Ce（Ru1-xFex）2Al 10（x=0 to 1）中的竞争4f电子动力学：近藤半导体态的磁有序
Competing 4f-electron dynamics in Ce(Ru1-xFex)2Al10 (x=0 to 1): magnetic ordering emerging from the Kondo semiconducting state
摘要：
我们对Ce（Ru_（1-x）Fex）_2Al_（10）（x=0，0.3，0.5，0.8和1）多晶样品进行了μ子自旋弛豫（muSR）、中子衍射和非弹性中子散射（INS）研究，以研究端元中的体测量所表明的基态（磁有序与顺磁）的性质和自旋能隙形成的起源。我们的零场muSR谱清楚地揭示了相干双频振荡在低温下在x=0，0.3和0.5的样品，这证实了长程磁有序的Ce-时刻TN=27，26和21 K分别。另一方面，x=0.8和x=1下至1.4 K和0.045 K的muSR谱分别表现出与温度无关的Kubo-Toyabe项，证实了顺磁基态。通过中子衍射研究证实了21 K以下x=0.5的长程磁有序。x=0的INS测量清楚地揭示了在5 K和26 K之间在8 meV附近存在尖锐的非弹性激发，这是由于自旋激发光谱中的间隙的打开，其在30 K及以上转变为宽响应。有趣的是，在4.5 K下，自旋能隙激发在x=0.3处变宽，并且在x=0.5处在8.4（3）和12.0（5）meV处显示出两个清晰的峰。在x=0.8的样品中，其在低至1.2 K时保持顺磁性，在7 K时存在10-12 meV的自旋能隙的明显特征，具有强的Q依赖强度。在x=1的情况下也发现了12.5（5）meV的自旋能隙的证据。在顺磁性样品（x=0.8和1）的自旋间隙的观察是一个有趣的发现，在这项研究中，它挑战了我们的理解的起源CeT 2Al 10（T=Ru和Os）化合物的半导体间隙的杂交间隙开放只有一小部分的费米面，带隙的自旋波，或自旋二聚体间隙。
英文摘要：
We have carried out muon spin relaxation (muSR), neutron diffraction and inelastic neutron scattering (INS) investigations on polycrystalline samples of Ce(Ru1-xFex)2Al10 (x=0, 0.3, 0.5, 0.8 and 1) to investigate the nature of the ground state (magnetic ordered versus paramagnetic) and the origin of the spin gap formation as evident from the bulk measurements in the end members. Our zero-field muSR spectra clearly reveal coherent two-frequency oscillations at low temperature in x=0, 0.3 and 0.5 samples, which confirms the long-range magnetic ordering of the Ce-moment with TN=27, 26 and 21 K respectively. On the other hand the muSR spectra of x=0.8 and x=1 down to 1.4 K and 0.045 K, respectively exhibit a temperature independent Kubo-Toyabe term confirming a paramagnetic ground state. The long-range magnetic ordering in x=0.5 below 21 K has been confirmed through the neutron diffraction study. INS measurements of x=0 clearly reveal the presence of a sharp inelastic excitation near 8 meV between 5 K and 26 K, due to an opening of a gap in the spin excitation spectrum, which transforms into a broad response at and above 30 K. Interestingly, at 4.5 K the spin gap excitation broadens in x=0.3 and exhibits two clear peaks at 8.4(3) and 12.0(5) meV in x=0.5. In the x=0.8 sample, which remains paramagnetic down to 1.2 K, there is a clear signature of a spin gap of 10-12 meV at 7 K, with a strong Q-dependent intensity. Evidence of a spin gap of 12.5(5) meV has also been found in x=1. The observation of a spin gap in the paramagnetic samples (x=0.8 and 1) is an interesting finding in this study and it challenges our understanding of the origin of the semiconducting gap in CeT2Al10 (T=Ru and Os) compounds in terms of hybridization gap opening only a small part of the Fermi surface, gapped spin waves, or a spin-dimer gap.
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