Tuning the static and dynamic magnetization properties of exchange bias modulated thin films

Aiming for new magnetic properties, the lateral combination of different magnetic properties into hybrid magnetic thin film structures are of increasing interest. We investigated exchange bias patterned thin NiFe/IrMn films to correlate the static and dynamic magnetization processes of the artificial hybrid material to the intrinsic material properties. Arrays of stripes with modulated exchange bias, i.e. exchange bias strength and direction, and a periodicity of a few micrometers were created. Inductive magnetometry revealed a distinct influence of geometry and orientation on the magnetization loop yielding either single-step shifted hysteresis loops or two-step loops with exchange spring effect. By means of high resolution Kerr microscopy, this could be attributed to either coherently or separately reversed stripe magnetization. As for the dynamics, the films exhibited either multiple resonance frequencies (as superposition of the input properties) or a single hybrid resonance frequency. The acquired frequencies at zero bias field as well as according damping parameters could be varied by a factor of about two. The different phenomena are discussed in terms of direct exchange coupling via the extended NiFe film as well as quasi-magnetostatic interactions at the stripe interfaces.