Time resolved pump probe experiments with ultra short infrared pump and x-ray photoemission probe pulses require a stable magnetic reference system with reproducible magnetic properties. In search of such a system we found in iron on tungsten an ideal sample. The coercive field of this system remains constant at 12.2±1 Oe between 15 and 25 monolayers. Kerr effect measurements and scanning electron microscopy with polarization analysis images prove that the magnetization switches from single domain to single domain state. Capping with Au increases the coercive field and prevents the Fe layer from deterioration.