Kondo screening and beyond: An x-ray absorption and dichroism study of CePt5/Pt(111)

Article

关键词: SPIN SUM-RULE;    CIRCULAR-DICHROISM;    CE;    SURFACE;    BEHAVIOR;    SPECTRA;    ALLOYS;    BANDS;    ORDER;    FIELD;   

DOI  :  10.1103/PhysRevB.95.115113

来源: SCIE

【 摘 要 】

We use x-ray absorption spectroscopy as well as its linear and circular magnetic dichroisms to characterize relevant interactions and energy scales in the surface intermetallic CePt5/Pt(111). The experiments provide insight into crystal field splitting, effective paramagnetic moments, their Kondo screening and mutual interactions, and thus into many aspects which typically determine the low-temperature behavior of correlated rare-earth compounds. Exploiting the tunability of Ce valence through the thickness-dependent epitaxial strain at the CePt5/Pt(111) interface, we are able to systematically investigate the impact of hybridization strength on these interactions. Considerable Kondo screening is indeed observed at all CePt5 thicknesses, and found to be strongest in case of strongest hybridization. While the magnetic response is commensurate with an impurity Kondo scale of T-K greater than or similar to 10(2) K for specimen temperatures T greater than or similar to 30 K, this is no longer the case at lower temperature. Its detailed study by x-ray circular magnetic dichroism (XMCD) at one specific thickness of CePt5 reveals an anomaly of the susceptibility at T* approximate to 25 K instead, which we tentatively associate with the onset of lattice coherence. At lowest temperature we observe paramagnetic saturation with a small Ce 4f saturation magnetization. Within the framework of itinerant 4f electrons, saturation is due to a field-induced Lifshitz transition involving a very heavy band with correspondingly small degeneracy temperature of T-F approximate to 7 K. This small energy scale results in the persistence of Curie-Weiss behavior across the entire range of experimentally accessible temperatures (T greater than or similar to 2 K). Our work highlights the potential of magnetic circular dichroism studies in particular for Kondo and heavy-fermion materials, which so far has remained largely unexplored.

【 授权许可】

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