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Part B: Condensed Matter Physics

Role of Ce 4f-conduction band on-site hybridisation in the nature of magnetism in Ce5MGe2, where M is d-electron-type metal

Pages 1193-1203 | Received 17 Mar 2019, Accepted 04 Sep 2019, Published online: 05 Oct 2019
 

ABSTRACT

A combined experimental study and band structure calculations indicate a mixed valence of Ce in the series of Ce5MGe2 compounds (M= Ru, Rh, Pd, and Ag), due to strong on-site hybridisation (Vfc) between Ce 4f states and conduction band, which is a reason for their complex magnetic structure. It has been shown that energy Vfc is 50 meV and does not significantly depend on metal M. In effect, the Curie temperatures of these compounds are very similar (TC14 K). However, Vfc is strongly modified by local atomic environment of Ce ions. The same, exchange interaction between various Ce ions depends on random occupation in the vicinity of Ce sites, which can be cause of spin glass-like state (Tf) in the Ce5MGe2 series. On the basis of Schrieffer–Wolff transformation, ab initio calculations and x-ray photoelectron spectroscopy (XPS) data, we estimated Jfs coupling constants for a Ce5MGe2 series, which are dependent on Wyckoff position of Ce and its atomic environment. We argue that various Jfs are a reason of spin glass-like state in each compound. For Ce5RuGe2, Ce5RhGe2 and Ce5PdGe2, the interband hybridisation forms a pseudogap in density of states (DOS) at the Fermi level, which could be reason of a Mott variable-range hoping behaviour.

Disclosure statement

No potential conflict of interest was reported by the authors.

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