TY - JOUR
T1 - Critical Role of W Insertion Layer Sputtering Condition for Reference Layer on Magnetic and Transport Properties of Perpendicular-Anisotropy Magnetic Tunnel Junction
AU - Honjo, Hiroaki
AU - Ikeda, Shoji
AU - Sato, Hideo
AU - Yasuhira, Mitsuo
AU - Endoh, Tetsuo
N1 - Funding Information:
ACKNOWLEDGMENT This work was supported in part by CIES’s Industrial Affiliation on the STT MRAM Program, in part by CIES Consortium, in part by JST-ACCEL, Japan, under Grant JPMJAC1301, and in part by JST-OPERA.
PY - 2019/7
Y1 - 2019/7
N2 - We investigated an effect of sputtering gas species Ar, Kr, and Xe for deposition of a W insertion layer W(Ar, Kr, and Xe) in the synthetic ferrimagnetic reference layer consisting of [Co/Pt] multilayer/Ru/[Co/Pt] multilayer/W/CoFeB on magnetic properties of the reference layer and tunnel magnetoresistance ratio (TMR ratio) of magnetic tunnel junction (MTJ) stacks with the reference layer. In all the cases, the TMR ratio increased with the increase of the W insertion layer thickness tW and showed a maximum at certain tW. Although the maximum TMR ratio is almost the same for all the cases, tW range in which we observed the maximum TMR ratio is dependent on the gas species; tW = 0.2 nm for Ar, tW = 0.2-0.4 nm for Kr, and tW = 0.2-0.5 nm for Xe, indicating that tW margin giving high-TMR ratio becomes wider with increasing atomic number of the gas species. The lower TMR ratio for W (Ar) at larger tW region is due to the degradation of ferromagnetic coupling between the CoFeB and Co/Pt multilayer sandwiching W, resulting in canting of magnetization in the CoFeB layer. We found that an intermixing of Pt atoms in the Co/Pt multilayer occurred in the MTJ stack with W (Ar), whereas it did not intermix with W (Kr), indicating that the Pt interdiffusion caused the degradation of ferromagnetic coupling through W layer.
AB - We investigated an effect of sputtering gas species Ar, Kr, and Xe for deposition of a W insertion layer W(Ar, Kr, and Xe) in the synthetic ferrimagnetic reference layer consisting of [Co/Pt] multilayer/Ru/[Co/Pt] multilayer/W/CoFeB on magnetic properties of the reference layer and tunnel magnetoresistance ratio (TMR ratio) of magnetic tunnel junction (MTJ) stacks with the reference layer. In all the cases, the TMR ratio increased with the increase of the W insertion layer thickness tW and showed a maximum at certain tW. Although the maximum TMR ratio is almost the same for all the cases, tW range in which we observed the maximum TMR ratio is dependent on the gas species; tW = 0.2 nm for Ar, tW = 0.2-0.4 nm for Kr, and tW = 0.2-0.5 nm for Xe, indicating that tW margin giving high-TMR ratio becomes wider with increasing atomic number of the gas species. The lower TMR ratio for W (Ar) at larger tW region is due to the degradation of ferromagnetic coupling between the CoFeB and Co/Pt multilayer sandwiching W, resulting in canting of magnetization in the CoFeB layer. We found that an intermixing of Pt atoms in the Co/Pt multilayer occurred in the MTJ stack with W (Ar), whereas it did not intermix with W (Kr), indicating that the Pt interdiffusion caused the degradation of ferromagnetic coupling through W layer.
KW - CoFeB-MgO
KW - double-interface structure
KW - interfacial anisotropy
KW - magnetic tunnel junction (MTJ)
KW - perpendicular anisotropy
KW - spin-transfer torque magnetoresistive random access memory
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U2 - 10.1109/TMAG.2019.2897067
DO - 10.1109/TMAG.2019.2897067
M3 - Article
AN - SCOPUS:85067859040
VL - 55
JO - IEEE Transactions on Magnetics
JF - IEEE Transactions on Magnetics
SN - 0018-9464
IS - 7
M1 - 8676124
ER -