Effect of rapid thermal heating on the unidirectional exchange anisotropy of Ni81Fe19/FeMn system with very thin Ni81Fe19 layers

The unidirectional exchange anisotropy field, H_ua, of NiFe(t_NiFe)/FeMn(15 nm) with very small t_NiFe from 3 nm to 25 nm was studied by heating the NiFe films using an in-situ rapid thermal heater during sputtering. A critical NiFe film thickness of about 15 nm was found. When t_NiFe was below 15 nm, the H _ua of NiFe/FeMn films was enhanced by in-situ heating, compared with that of films deposited without heating. However, no significant difference of H_ua between the films with and without in-situ heating were observed for films with NiFe film thicker than 15 nm and the dependence of H_ua on NiFe film thickness roughly obeys 1/t_NiFe dependence. X-ray diffraction examination of these films suggests that a better epitaxial growth and improved crystallinity of the γ-FeMn(111)/NiFe(111) might be responsible for the enhanced H_ua at NiFe/FeMn interface