Structure and properties of mixed valent CeFe2Al8.

Abstract

Temperature dependent magnetic, electrical transport and thermal properties of polycrystalline orthorhombic CeFe₂Al₈intermetallic compound have been studied along with its isostructural La counterpart, LaFe₂Al₈. For the cerium compound, low fielddcmagnetization exhibits an antiferromagnetic like ordering (T_N) ∼ 4 K. The main feature of the magnetic susceptibility plot is a broad hump spanning a large temperature range, indicating mixed valence of Ce in the compound, in good agreement with reported literature. However, contrary to the reported observations we find that the mixed valence state is very robust and was evident even up to very high magnetic fields (> 2 T). Further, in this work we report 3d core level photoemission spectra of cerium in CeFe₂Al₈, to understand the valence state of cerium ions in this system. Additionally, from resistivity measurements it is found that, CeFe₂Al₈is metallic with no indication of any anomaly, till the lowest temperature of measurement. Specific heat measurements show very low value of heat capacity and electronic contribution. The isostructural La analogue, LaFe₂Al₈compound shows broadness in susceptibility with maxima around 44 K which may be attributed to ordering of Fe moments. The comparison of Ce and La compounds brings out the role of Fe magnetic moments which may be responsible for competing with cerium moments and resulting in the dilution of long-range magnetic order, also contributing to magnetic frustration in CeFe₂Al₈.