MAGNETIC-ORDERING AND KONDO COMPENSATION IN THE TERNARY HEAVY-FERMION COMPOUND CECU5AU

The new ternary compound CeCu5Au is derived from the heavy-fermion system CeCu6 by replacing the Cu(2) site by Au. Measurements of the dc magnetization, the specific heat, the magnetocaloric effect, and the electrical resistivity on Czochralski-grown single crystals reveal a complex (B, T) phase diagram with probably two antiferromagnetic phases and one spin-flop phase. The Neel temperature was determined to T(N) = 2.3 K. The magneto-resistance exhibits several features which can partly be explained by the different antiferromagnetic phases. In addition to the antiferromagnetic order the observation of a large specific heat at very low temperatures (gamma = C/T = 0.64 J/molK2 at T = 0.1 K) indicates the coexistence of antiferromagnetism and Kondo compensation. An analysis of the specific heat using the resonance-level model yields a Kondo temperature of T(K) = 1.8 K. The analysis for lower fields is complicated by the presence of magnetic order. In terms of a homogeneous model, T(K) = 1.0 K for B = 0 is inferred. The increase of T(K) with field and also the concentration dependence of T(K) can be qualitatively explained.