On the random antiphase state in the ± J spin glass model in two dimensions

Numerical calculations of a ground state and the rigidity have been made for samples of 50 × 50 Ising spins interacting via ± J bonds on a square lattice using Edmond's algorithm, a method well established in optimization theory. For some value of the concentration (0.1<x<0.2) of antiferromagnetic bonds (-J), an ordered (rigid) state occurs with zero magnetization due to magnetic wall separating domains of opposite spins. This new phase, here named a random antiphase state, could be an intermediate phase between ferromagnetism and paramagnetism.