Field mapping and temperature dependence of magnetic domain memory induced by exchange couplings

Abstract

Strong magnetic domain memory is achieved in [Co/Pd]IrMn exchange-biased ferromagnetic thin films when zero-field-cooled (ZFC) below their blocking temperature TB. By mapping out the amount of memory throughout the entire magnetization cycle, from nucleation to saturation, at different temperatures below and above TB, 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.