MAGNETIC-ORDERING AND KONDO COMPENSATION IN THE TERNARY HEAVY-FERMIONCOMPOUND CECU5AU

The new ternary compound CeCu5Au is derived from the heavy-fermion sys tem CeCu6 by replacing the Cu(2) site by Au. Measurements of the dc ma gnetization, the specific heat, the magnetocaloric effect, and the ele ctrical resistivity on Czochralski-grown single crystals reveal a comp lex (B, T) phase diagram with probably two antiferromagnetic phases an d one spin-flop phase. The Neel temperature was determined to T(N) = 2 .3 K. The magneto-resistance exhibits several features which can partl y be explained by the different antiferromagnetic phases. In addition to the antiferromagnetic order the observation of a large specific hea t at very low temperatures (gamma = C/T = 0.64 J/molK2 at T = 0.1 K) i ndicates the coexistence of antiferromagnetism and Kondo compensation. An analysis of the specific heat using the resonance-level model yiel ds 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 homoge neous 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 qualit atively explained.