  Many-body systems subject to a high-frequency drive can show intriguing
thermalization behavior. Prior to heating to a featureless infinite-temperature
state, these systems can spend an exponentially long time in prethermal phases
characterized by various kinds of order. Here, we uncover the rich
non-equilibrium phase diagram of a driven frustrated two-dimensional Ising
magnet with competing short-range ferromagnetic and long-range dipolar
interactions. We show that the ordered stripe and nematic phases, which appear
in equilibrium as a function of temperature, underpin subsequent prethermal
phases in a new multi-step heating process en route towards the ultimate heat
death. We discuss implications for experiments on ferromagnetic thin films and
other driving induced phenomena in frustrated magnets.
