The magnetotransport properties of Fe4 NMgOCoFeB and Fe/MgO/CoFeB magnetic tunnel junctions (MTJs) were investigated at room temperature. In the Fe/MgO/CoFeB-MTJ, normal tunnel magnetoresistance (TMR) effect and roughly symmetric bias voltage (VB) dependence were observed, similar to the MTJs exhibiting coherent tunneling such as Fe/MgO/Fe. On the other hand, the inverse TMR effect, showing higher tunnel resistance for parallel magnetization configuration than for antiparallel configuration, and strong asymmetric VB dependence of TMR ratio were observed in the Fe4 NMgOCoFeB -MTJ. The maximum TMR magnitude of 18.5% was obtained at VB =-200 mV, where the current flows from Fe4 N to CoFeB. The enhancement of the inverse TMR ratio around VB =-200 mV is due to the broad peak of tunnel conductance in antiparallel configuration of Fe4 N and CoFeB magnetizations. A large peak of the density of state at +300 meV from the Fermi level for minority spin electrons of bulk Fe4 N might be an origin of this phenomenon.
ASJC Scopus subject areas
- Physics and Astronomy(all)