We present specific heat, electrical resistivity, susceptibility, and thermopower measurements on the two novel intermetallic compounds CeFe2Al8 and CeCo2Al8. They form in an orthorhombic crystal structure of space group Pbam. In the unit cell representation Ce atom occupies only one lattice site,having Ce-Ce interatomic distance of 4.03Å. Magnetic susceptibility of CeFe2Al8 in the range of 1.9K - 400K yields an effective paramagnetic moment value of 3.89μB together with prevailing antiferromagnetic interaction through Weiss temperature Θ=-745.8K. The overall temperature dependence suggests valence instability in this compound and we model the appearance of broad peak around T=230K in the susceptibility to a T2lnT dependence attributed to an intermediate valent state. On the other hand for CeCo2Al8 the local moment state is depicted through an effective moment close to the free Ce3+ ion value. No long-range magnetic ordering is found in either of the two compounds down to 1.9K. The magnetic contribution of electrical resistivity on CeFe2Al8 and CeCo2Al8 compounds follows –lnT behavior at intermediate temperatures which is typical of incoherent Kondo interactions between conduction electrons and magnetic Ce ions. A Fermi liquid behavior in resistivity measurement is observed in CeFe2Al8 compound towards the ground state,whereas clear deviations from standard Fermi liquid behavior are indicative of strong electronic correlation effects in CeCo2Al8. At 2K the electronic specific heat of this compound reaches γ =0.106J/mol-K2,and exhibits a –lnT divergence towards T→0. We explain this behavior in terms of quantum criticality that stems from low-lying magnetic ordering effects. In studies of the thermoelectric power,a maximum is reached at T=140K(S=24μV/K) and T=30K(S=23μV/K) for CeFe2Al8 and CeCo2Al8 compounds respectively. We propose a description for this behavior in terms of formation of fine structure in the electronic density of states near the Fermi energy(EF).
|Level (Hons, MSc, <br> PhD, other)?||PhD Physics|
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