ABSTRACT
A combined experimental study and band structure calculations indicate a mixed valence of Ce in the series of CeGe
compounds (
Ru, Rh, Pd, and Ag), due to strong on-site hybridisation (
) between Ce
states and conduction band, which is a reason for their complex magnetic structure. It has been shown that energy
is
meV and does not significantly depend on metal M. In effect, the Curie temperatures of these compounds are very similar (
K). However,
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 (
) in the Ce
Ge
series. On the basis of Schrieffer–Wolff transformation, ab initio calculations and x-ray photoelectron spectroscopy (XPS) data, we estimated
coupling constants for a Ce
Ge
series, which are dependent on Wyckoff position of Ce and its atomic environment. We argue that various
are a reason of spin glass-like state in each compound. For Ce
RuGe
, Ce
RhGe
and Ce
PdGe
, 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.