MU-SR STUDY OF THE INTERMEDIATE HEAVY-FERMION SYSTEM CERUSI2

Zero-field (ZF), longitudinal field (LF), muon spin relaxation (mu SR) , and transverse field (TF) muon spin rotation (mu SR) measurements ha ve been carried out on a polycrystalline sample CeRuSi2. ZF data show a sharp increase in the muon relaxation rate below the temperature 12 K (0.42 mu s(-1) at T=4.2 K), justifying the transition to the magneti cally ordered state. From the LF measurements at T=4.2 K, we found tha t the magnetic fields on the muon, B-mu, produced by the cerium magnet ic moments are mainly static: The external longitudinal field of 150 G practically recovers muon spin polarization. In the paramagnetic phas e the polarization has an exponential form in the whole range of tempe ratures 20 K<T<300 K, but LF experiments at T=20 K show that there is a static contribution (-70%). This situation is discussed within the f ramework of the double-relaxation model. Hysteresis in (B-H) observed in the TF experiment and the results of magnetization measurements agr ee with ferromagneticlike ordering below T-C=11.6 K. The width of the field distribution obtained in the TF experiment corresponds to the or dered moment (0.005-0.05)mu(beta), depending on the assumed muon site.