Hydride phases, structure, and magnetic properties of the UNiAlH y system
Hydride phases, structure, and magnetic properties of the UNiAlH y system
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UNiAlH y 系统的氢化物相、结构和磁性
DOI：
10.1103/physrevb.63.094414
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
S. Malik
中科院分区：
文献类型：
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作者：
P. Raj;K. Shashikala;A. Sathyamoorthy;N. Kumar;C. Rao;S. Malik
本文研究了重费米子化合物UNiAl的双折射行为。具有正交结构（空间群Pnma）的一系列氢化物组合物已经稳定。因此，一个不同的命名为UNiAlHy氢化物相的建议。X射线衍射和磁性研究报告的三种组合物在这个范围内，即，y=0.06、0.14和0.58。所有这些组合物不显示磁有序下降到2 K，虽然弱铁磁相关是显而易见的，在他们的磁性研究。在这些情况下，铀原子上的低有效矩值，略低于巡游反铁磁UNiAl的值，表明U 5 f电子的巡游特性增加。我们还报告了六方晶系UNiAlHy（y=0.7）的磁化研究。在87 K以下表现出铁磁有序性。这意味着在六方氢化物相中，磁有序的性质从反铁磁性（y=0）变为铁磁性（y=0.7），当y=2.3时又回到反铁磁性。结果表明，六方氢化物相（y = 0.7和2.0-2.5）中铀原子的磁矩接近自由离子的局域磁矩。
The hydriding behavior of the heavy fermion compound UNiAl has been investigated. A range of hydride compositions with orthorhombic structure (space group Pnma) has been stabilized. As a result, a different nomenclature for the UNiAlH y hydride phases is proposed. X-ray diffraction and magnetic studies are reported on three compositions in this range of hydrides, viz., y=0.06, 0.14, and 0.58. All these compositions do not show magnetic ordering down to 2 K, though weak ferromagnetic correlations are apparent in their magnetic studies. Low effective moment values on uranium atoms in these cases, appreciably below the value for itinerant antiferromagnetic UNiAl, indicate increased itinerant character of U 5f electrons. We also report magnetization studies on hexagonal UNiAlH y (y=0.7). It shows ferromagnetic ordering below 87 K. This means that in the hexagonal hydride phases, the nature of magnetic ordering changes from antiferromagnetic (y=0) to ferromagnetic (y=0.7) and again back to antiferromagnetic for y=2.3. It is shown that the moment on the uranium atoms in the hexagonal hydride phases (y≅0.7 and 2.0-2.5) is close to the free-ion local moment value.