Enhancement of Exchange Bias in the ${\rm Co}_{2}{\rm FeSi/IrMn}$ System

The structural and magnetic properties of sputtered polycrystalline Co₂FeSi (CFS) thin films have been studied. A combination of magnetometry, X-ray diffraction, and X-ray photon spectrometry have been used to measure the changes in magnetization, coercivity, grain size and compositional depth profile as a function of annealing conditions and seed-layer choice. The CFS thin films displayed an ordered B2 structure when deposited on a Cr seed layer and annealed at 573 K. Further increases in annealing temperature were found to disrupt the crystallinity of the CFS and lead to Si segregation at the interface. After obtaining an optimized growth process, a study of the exchange biasing of CFS with the antiferromagnetic (AF) IrMn was made. A 15% enhancement of the exchange bias of CFS was found when an ultra-thin-layer CoFe was added at the CFS/IrMn interface due to an increase in the strength of the interfacial coupling.