Effects of random biquadratic couplings in a spin-1 spin-glass model

A spin-1 model, appropriated to study the competition between bilinear (J(i j)S(i)S(j)) and biquadratic ((KijSiSj2)-S-2) random interactions, both of t hem with zero mean, is investigated. The interactions are infinite-ranged a nd the replica method is employed. Within the replica-symmetric assumption, the system presents two phases, namely, paramagnetic and spin-glass, separ ated by a continuous transition line. The stability analysis of the replica -symmetric solution yields, besides the usual instability associated with t he spin-glass ordering, a new phase due to the random biquadratic couplings between the spins.