Most studies on exchange bias in spin valves are for antiferromagnetic/ ferromagnetic structures, and Fe  Mn  Ni  Fe  is widely used. The results of the exchange-bias field (Hex) and coercivity (Hc) as a function of the annealing temperature in NiFeFeMn and FeMnNiFe systems are given in the study. We prepare two types of films, type I: substrate/ TaNiFeFeMnTa and type II: substrate/ TaFeMnNiFeTa, respectively. Annealing was performed at 150-450 °C under 720 Oe for 2 h, Hex and Hc of type I samples increase slightly with the increase of the annealing temperature. But Hex and Hc of type II samples increase rapidly after annealing over 300 °C, then decrease after annealing at 375 °C. The strong exchange-bias field and low coercivity were exhibited for type I samples, where NiFe is the buffer layer and is also the pinned layer. In type II samples, the increase in the exchange-bias field is attributed to the altered interface of FeMnNiFe due to interdiffusion. The interpretation of the fluctuation of the magnetic properties for these two types of films in connection with the crystalline texture and morphology by x-ray scattering technologies as well as atomic force microscopy was given. This research leads to a better understanding of the annealing temperature and microstructures in the two types of bilayers.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)