Florida State University, Tallahassee, FL 32310-3706, USA.
Proc Natl Acad Sci U S A. 2010 Sep 7;107(36):15704-7. doi: 10.1073/pnas.1009498107. Epub 2010 Aug 23.
Metallic magnetism is both ancient and modern, occurring in such familiar settings as the lodestone in compass needles and the hard drive in computers. Surprisingly, a rigorous theoretical basis for metallic ferromagnetism is still largely missing. The Stoner approach perturbatively treats Coulomb interactions when the latter need to be large, whereas the Nagaoka approach incorporates thermodynamically negligible holes into a half-filled band. Here, we show that the ferromagnetic order of the Kondo lattice is amenable to an asymptotically exact analysis over a range of interaction parameters. In this ferromagnetic phase, the conduction electrons and local moments are strongly coupled but the Fermi surface does not enclose the latter (i.e., it is "small"). Moreover, non-Fermi-liquid behavior appears over a range of frequencies and temperatures. Our results provide the basis to understand some long-standing puzzles in the ferromagnetic heavy fermion metals, and raise the prospect for a new class of ferromagnetic quantum phase transitions.
金属磁性既古老又现代，存在于罗盘指针中的天然磁石和计算机硬盘等常见环境中。令人惊讶的是，金属铁磁性的严格理论基础在很大程度上仍然缺失。当库仑相互作用需要很大时，斯通纳方法会微扰处理它们，而永田方法则将热力学上可以忽略不计的空穴纳入半满带。在这里，我们表明，近藤晶格的铁磁性可以在一系列相互作用参数范围内进行渐近精确分析。在这个铁磁相中，传导电子和局域磁矩强烈耦合，但费米面不包含后者（即，它是“小”的）。此外，非费米液体行为出现在一系列频率和温度范围内。我们的结果为理解铁磁重费米子金属中一些长期存在的难题提供了基础，并为一类新的铁磁量子相变提供了前景。
