  We study the remanent magnetization in antiferromagnetic, many-body localized
quantum spin chains, initialized in a fully magnetized state. Its long time
limit is an order parameter for the localization transition, which is readily
accessible by standard experimental probes in magnets. We analytically
calculate its value in the strong-disorder regime exploiting the explicit
construction of quasi-local conserved quantities of the localized phase. We
discuss analogies in cold atomic systems.
