To obtain low switching field (Hsw) we introduced amorphous ferromagnetic Co70.5 Fe4.5 Si15 B10 single and synthetic antiferromagnet (SAF) free layers in magnetic tunnel junctions (MTJs). The switching characteristics for MTJs with structures SiSi O2 Ta 45/Ru 9.5/IrMn 10/CoFe 7Al Ox CoFeSiB 7 or CoFeSiB (t) Ru 1.0/CoFeSiB (7-t) Ru 60 (in nanometer) were investigated and compared to MTJs with Co75 Fe25 and Ni80 Fe20 free layers. CoFeSiB showed a lower saturation magnetization of 560 emu cm3 and a higher anisotropy constant of 2800 erg cm3 than CoFe and NiFe, respectively. An exchange coupling energy (Jex) of -0.003 erg cm2 was observed by inserting a 1.0 nm Ru layer in between CoFeSiB layers. In the CoFeSiB single and SAF free layer MTJs, it was found that the size dependence of the Hsw originated from the lower Jex experimentally and by micromagnetic simulation based on the Landau-Lisfschitz-Gilbert equation. The CoFeSiB SAF structures showed lower Hsw than that of NiFe, CoFe, and CoFeSiB single structures. The CoFeSiB SAF structures were proved to be beneficial for the switching characteristics such as reducing the coercivity and increasing the sensitivity in micrometer- to submicrometer-sized elements.
ASJC Scopus subject areas
- Physics and Astronomy(all)