X-ray absorption spectra and self-bias ferromagnetic resonance of FeCoB films prepared by composition gradient sputtering

In this study, Fe_0.7Co_0.3-B SMFs were prepared by CGS method, where B as a doping element distributes in sample with a gradient content increasing from 24.41 to 30.85 at .% for the test positions n from one terminal to the other, undergoing CB=22.8+1.61×n (at .%) . X-ray absorption spectra, shown in Fig . 1, demonstrates that the B doping atoms hybridize with Fe atoms, instead of alloying, as a result, with the increase of B content, Fe³⁺ atomic ratio increases considerably, leading to a decrease of saturation magnetization 4πMS from 16 .3 to 13 .5 kG (Fig . 2a) . However, the uniaxial magnetic anisotropy fields HK of the SMFs dramatically increase from 180.6 to 295.5 Oe, as a result, the ferromagnetic resonance frequency fFMR is driven from 4 .82 to 5 .62 GHz (Fig . 2b) . Figure 2b reveals that the ferromagnetic resonance is dominated by magnetic anisotropy field HK . Acknowledgments This work was financially supported by NSFC 11074040 and ZR2012FZ006 . The XAS was detected at BL08U1A beam station of Shanghai Synchrotron Radiation Facility .