Non-universal Dynamics of Three-Dimensional Magnetic Systems With Heisenberg Interaction*

We numerically investigate the non-equilibrium critical dynamics in three-dimensional isotropic Heisenberg antiferromagnets. To account for the reversible terms arising from the microscopic dynamics of the system, we employ a hybrid simulation algorithm that combines reversible spin precession with relaxational Kawasaki spin exchange processes. We verify the dynamic exponent, and obtain a suitable aging scaling window. We observe and thus validate an older renormalization group prediction that, while the critical aging collapse exponent assumes universal value, the temporal decay exponent is found to be non-universal and dependent on the initial distribution of the spins.