Critical aspects of three-dimensional anisotropic spin-glass models

We study the three-dimensional ± J Ising model with a longitudinal anisotropic bond randomness on the simple cubic lattice. The random exchange interaction is applied only in the z direction, whereas in the other two directions, xy-planes, we consider ferromagnetic exchange. By implementing an effective parallel tempering scheme, we outline the phase diagram of the model and compare it to the corresponding isotropic one. We present a detailed finite-size scaling analysis of the ferromagnetic-paramagnetic and spin glass-paramagnetic transition lines, and we also discuss the ferromagnetic-spin glass transition regime. We conclude that the present model shares the same universality classes with the isotropic model, but at the symmetric point has a considerably higher transition temperature from the spin-glass state to the paramagnetic phase. Our data for the ferromagnetic-spin glass transition line support a forward behavior in contrast to the reentrant behavior of the corresponding isotropic model.