MAGNETIC PHASE-DIAGRAM OF GE-SUBSTITUTED CERU2SI2 IN AN APPLIED FIELD

Long-range magnetic order can be induced in the heavy-fermion compound CeRu2Si2 by slightly expanding its lattice through the substitution of a few percent of germanium for silicon. For a concentration z = 10%, the material orders in the same collinear, incommensurate, modulated structure as that already reported for (Ce,La)Ru2Si2. The (H,T) phase diagram of this system has been determined by elastic neutron scattering. Various commensurate-incommensurate transitions take place as a function of temperature and applied field. The results are discussed in connection with the problem of magnetic correlations in pure CeRu2Si2.