The advance of magnetic nanotechnologies relies on detailed understanding of nanoscale magnetic mechanisms in materials. Magnetic domain memory (MDM), that is, the tendency for magnetic domains to repeat the same pattern during field cycling, is important for magnetic recording technologies. Here we demonstrate MDM in [Co/Pd]/IrMn films, using coherent X-ray scattering. Under illumination, the magnetic domains in [Co/Pd] produce a speckle pattern, a unique fingerprint of their nanoscale configuration. We measure MDM by cross-correlating speckle patterns throughout magnetization processes. When cooled below its blocking temperature, the film exhibits up to 100% MDM, induced by exchange-coupling with the underlying IrMn layer. 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. Our findings show how to fully control the occurrence of MDM by field cooling.

Strong magnetic domain memory is achieved in [Co/Pd]IrMn exchange-biased ferromagnetic thin films when zero-field-cooled (ZFC) below their blocking temperature T B . By mapping out the amount of memory throughout the entire magnetization cycle, from nucleation to saturation, at different temperatures below and above T B , we discover how microscopic morphological changes in the magnetic domain patterns correlate with the macroscopic magnetic hysteresis, in the presence or absence of exchange couplings. Our unique inter-field correlation maps show that in the ZFC state, the film exhibits the highest amount of domain memory, exceeding 90%, when domain patterns are compared at the same field value, in the coercive region of the magnetization loop. However, domain patterns also cross-correlate surprisingly well when measured at different field values, on a wide field range centered about the coercive region. The shape and symmetry of the correlation maps provide further insights into the microscopic morphological changes in the domain patterns and the amount of reversibility in the reversal process, at the nanoscale.