Strongly Correlated Electron Behaviour in CeT₂Al₈(T = Fe, Co)

Abstract

We report on studies of physical properties of the two compounds CeFe2Al8 and CeCo2Al8 in which we have found varying degrees of electronic correlational phenomena. No magnetic ordering was detected down to 0.4 K in either of the two compounds. At elevated temperatures an incoherent Kondo interaction between the Ce 4f -electron and the conduction electrons is prevalent in both compounds. CeCo2Al8 exhibits a stable 4f -electron magnetic moment, but in CeFe2Al8 an intermediate-valent state prevails near room temperature that eventually transforms into a Fermi-liquid ground state. The low-temperature specic heat of CeCo2Al8 shows typical strongly correlated electron behaviour and a − log T upturn in its electronic specic heat below about 10 K.

Magnetic ordering and crystal field effects in quasi-caged structure compound PrFe2Al8

“…The structural peculiarities comprising of the quasi cage-like structure of Al polyhedra and the strand-like alignment of Pr and T along the c-axis are of key significance. Among the various RT 2 X 8 compounds investigated, the Ce-based compounds CeFe 2 Al 8 and CeCo 2 Al 8 displayed no signature of magnetic ordering down to 0.4 K [7]. These compounds were investigated for the strongly correlated electron behaviour.…”

“…In the case of 1:1:5 and 2:1:8-stoichiometries, the R-ion is in the trivalent f 1 (Ce) state whereas in 1:2:8 systems, the rare earth is in divalent or mixed-valent state [5]. In Ce-based 1:2:8 systems, [1,6,7] Fermi-liquid with proximity to long-range magnetic order [7]. Cerium based RT 2 X 8 with X = Al, Ga have been reported previously also [1,10] on which Mößbauer spectroscopy [1] and neutron diffraction studies [6] were performed in order to understand the magnetic ground state.…”

Strategic Crystal Growth and Physical Properties of Single-Crystalline LnCo2Al8 (Ln = La–Nd, Sm, Yb)

“…Ce is trivalent in CeCo 2 Al 8 , while Ce is valence fluctuating in CeFe 2 Al 8 . 11 Because the oxidation state of Ce in CeM 2 Al 8 (M = Fe, Co) is dependent on the transition metal, we investigated the incorporation of Mn, Fe, and Ni in CeCo 2 Al 8 , where we observed Ce fluctuating valence in CeCo 2-x Fe x Al 8 (x ~ 1.00), as we moved closer to the endmember of CeFe 2 Al 8 . 12 To grow larger single crystals necessary for physical property measurements, we set out to determine the best conditions for synthesis of LnCo 2 Al 8 (Ln = LaNd, Yb).…”

“…10 With our interest in highly correlated systems, we sought out to grow single crystals of CeM 2 Al 8 (M = Fe, Co). 11 The oxidation state of Ce in CeM 2 Al 8 (M = Fe, Co) is highly dependent on the transition metal. Ce is trivalent in CeCo 2 Al 8 , while Ce is valence fluctuating in CeFe 2 Al 8 .…”

Reinvestigation of the Ce–Co–Al ternary system: Isothermal section at 973K

“…CeCo 2 Al 8 is a non magnetic Kondo compound [7]. Ce 2 Co 6 Al 19 is also non magnetic and exhibits a non-Fermi liquid behavior [8].…”