SPIN-GLASS MODEL WITH UNIFORM BIQUADRATIC INTERACTIONS

We study a spin-1 infinite-ranged Ising spin-glass model with uniform biquadratic exchange interactions. The phase diagram of the model is o btained in the framework of the replica-symmetric solution. For the ca se of attractive biquadratic interactions the usual spin-glass phase i s stabilized at low temperatures, but for the repulsive case, the anti quadrupolar and antiquadrupolar-glaas phases with two-sublattice struc ture are also possible. We investigate the stability of the replica-sy mmetric solution and show that the paramagnetic and antiquadrupolar ph ases are stable, whereas the spin-glass and antiquadrupolar-glass phas es are unstable. Parisi's replica-symmetry-breaking procedure is imple mented in the neighbourhood of the spin-glass-paramagnetic critical fr ontier.