Shaping nanoscale magnetic domain memory in exchange-coupled ferromagnets by field cooling

The advance of magnetic nanotechnologies relies on detailed understanding of nanoscale magnetic mechanisms in materials. Magnetic domain memory (MDM), i.e., the tendency for magnetic domains to repeat the same pattern during field-cycling, is important to many technologies including magnetic recording developments. We show coherent x-ray magnetic scattering studies unveiling MDM in [Co/Pd]/IrMn films. When illuminated by coherent x-rays, the magnetic domains in the [Co/Pd] multilayer produce a speckle pattern unique to their specific nanoscale configuration. By cross-correlating such speckle patterns throughout the magnetization loop, we measure the MDM. When cooled below its blocking temperature, the film exhibits up to 100% MDM, induced by exchange-couplings with the IrMn layer. Furthermore, the degree of MDM drastically depends on cooling conditions. If the film is cooled under moderate fields, MDM is high throughout the entire magnetization loop. If the film is cooled under nearly saturating field, MDM vanishes, except at nucleation and saturation