Effect of rapid thermal heating on the unidirectional exchange anisotropy of Ni/sub 81/Fe/sub 19//FeMn system with very thin Ni/sub 81/Fe/sub 19/ layers

The unidirectional exchange anisotropy field, H/sub ua/, of NiFe(t/sub N/iFe)/FeMn(15 nm) with very small t/sub 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/sub NiFe/ was below 15 nm, the H/sub 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/sub 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/sub ua/ on NiFe film thickness roughly obeys 1/t/sub NiFe/ dependence. X-ray diffraction examination of these films suggests that a better epitaxial growth and improved crystallinity of the /spl gamma/-FeMn(111)/NiFe(111) might be responsible for the enhanced H/sub ua/ at NiFe/FeMn interface.