Scaling of the magnetic linear response in phase-ordering kinetics

The scaling of the thermoremanent magnetization and of the dissipative part of the non-equilibrium magnetic susceptibility is analysed as a function of the waiting-time $s$ for a simple ferromagnet undergoing phase-ordering kinetics after a quench into the ferromagnetically ordered phase. Their scaling forms describe the cross-over between two power-law regimes governed by the non-equilibrium exponents $a$ and $\lambda_R/z$, respectively. A relation between $a$, the dynamical exponent $z$ and the equilibrium exponent $\eta$ is derived from scaling arguments. Explicit tests in the Glauber-Ising model and the kinetic spherical model are presented.