QUADRUPOLAR ORDERING IN CEAG

Several different couplings have been assumed in the past to meet in the cubic intermetallic compound CeAg: lattice instability of electronic origin, bilinear ferromagnetic interactions, Kondo-type coupling as well as quadrupole interactions. A review of lattice properties in the rare-earth-silver equiatomic compounds is presented here, in particular relating to the variation of the three cubic elastic modes across the series. The strength of the quadrupole interactions is then determined in the high-temperature phase of CeAg. Magnetization processes in the quadrupole and ferromagnetic phases are observed to be strongly dependent on the strain domain structure of the sample and to be very anisotropic due to quadrupole interactions. Calculations describe them in their mean features although the magnetic spontaneous moment is calculated a little larger than is observed (1. 67 mu //B instead of 1. 25 mu //B). This difference may be attributed to the band polarization, particularly large in rare-earth-silver equiatomic compounds, as well as to a Kondo-type effect.