Crystal electric field contribution to the thermoelectric power of the CeCoAl4 antiferromagnetic
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We report on the thermoelectric power S(T), electrical resistivity and thermal conductivity measurements on the antiferromagnetic CeCoAl<sub>4</sub> compound and on the nonmagnetic reference compound, LaCoAl<sub>4</sub>. The Neel temperature of CeCoAl<sub>4</sub> is T<sub>N</sub> = 13.5K and a metamagnetic-like transition occurs in the magnetic field of about 7.5T. We show that the magnetic contribution to the thermoelectric power, S<sub>f</sub> (T), exhibits a large peak due to the crystal electric field (CEF) at about 240K and a small anomaly around the ordering temperature. Surprisingly, the CEF related S<sub>f</sub> (T) peak is close to the upper CEF excitation energy \(\Delta_2\) = 202K, in contrast to the usual case of the peak position being located at a fraction of the observed CEF energy level. The applicability of different theoretical and phenomenological models describing the temperature dependence of the Seebeck effect S<sub>f</sub> (T) has been tested and finally a calculation is proposed, which incorporates a full CEF levels scheme.
