A spin-1 model, appropriated to study the competition between bilinear (J_{ ij}S_{ i}S_{ j}) and biquadratic (K_{ ij}S_{ i}^{ 2}S_{ j}^{ 2}) random interactions, both of them with zero mean, is investigated. The interactions are infinite-ranged and the replica method is employed. Within the replica-symmetric assumption, the system presents two phases, namely, paramagnetic and spin-glass, separated by a continuous transition line. The stability analysis of the replica-symmetric solution yields, besides the usual instability associated with the spin-glass ordering, a new phase due to the random biquadratic couplings between the spins.
Categories: cond-mat.stat-mech cond-mat.dis-nn