Research output: Contribution to journal › Article › peer-review
Defect-mediated properties of magnetic tunnel junctions. / Velev, J. P.; Zhuravlev, M. Ye; Belashchenko, K. D.; Jaswal, S. S.; Tsymbal, E. Y.; Katayama, T.; Yuasa, S.
In: IEEE Transactions on Magnetics, Vol. 43, No. 6, 01.06.2007, p. 2770-2775.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Defect-mediated properties of magnetic tunnel junctions
AU - Velev, J. P.
AU - Zhuravlev, M. Ye
AU - Belashchenko, K. D.
AU - Jaswal, S. S.
AU - Tsymbal, E. Y.
AU - Katayama, T.
AU - Yuasa, S.
PY - 2007/6/1
Y1 - 2007/6/1
N2 - Defects play an important role in the properties of metal oxides which are currently used as barrier layers in magnetic tunnel junctions (MTJs). We study the effect of O vacancies on the interlayer exchange coupling (IEC) and tunneling magnetoresistance (TMR) in Fe-MgO-Fe tunnel junctions. Measurements of IEC in fully epitaxial Fe-MgO-Fe(001) tunnel junctions show IEC is antiferromagnetic (AFM) for small MgO thickness but changes sign and then vanishes for large barrier thickness. First-principles calculations based on density functional theory demonstrate that the presence of neutral O vacancies (F-centers) in the MgO barrier can explain this behavior. Resonant tunneling through the F-centers makes IEC AFM for thin barriers but with increasing MgO thickness the resonance contribution to IEC is reduced resulting in the ferromagnetic (FM) coupling typical for perfect MgO barriers. First-principles calculations also show that O vacancies can affect TMR. F-centers produce occupied localized s-states and unoccupied resonant p-states in the gap of MgO. We demonstrate that F-centers affect the conductance by either resonant transmission or nonresonant scattering of tunneling electrons both causing a substantial reduction of TMR compared to the ideal case.
AB - Defects play an important role in the properties of metal oxides which are currently used as barrier layers in magnetic tunnel junctions (MTJs). We study the effect of O vacancies on the interlayer exchange coupling (IEC) and tunneling magnetoresistance (TMR) in Fe-MgO-Fe tunnel junctions. Measurements of IEC in fully epitaxial Fe-MgO-Fe(001) tunnel junctions show IEC is antiferromagnetic (AFM) for small MgO thickness but changes sign and then vanishes for large barrier thickness. First-principles calculations based on density functional theory demonstrate that the presence of neutral O vacancies (F-centers) in the MgO barrier can explain this behavior. Resonant tunneling through the F-centers makes IEC AFM for thin barriers but with increasing MgO thickness the resonance contribution to IEC is reduced resulting in the ferromagnetic (FM) coupling typical for perfect MgO barriers. First-principles calculations also show that O vacancies can affect TMR. F-centers produce occupied localized s-states and unoccupied resonant p-states in the gap of MgO. We demonstrate that F-centers affect the conductance by either resonant transmission or nonresonant scattering of tunneling electrons both causing a substantial reduction of TMR compared to the ideal case.
KW - Heterostructures
KW - Magnetic coupling
KW - Magnetic memories
KW - Magnetic recording
UR - http://www.scopus.com/inward/record.url?scp=34249021709&partnerID=8YFLogxK
U2 - 10.1109/TMAG.2007.893311
DO - 10.1109/TMAG.2007.893311
M3 - Article
AN - SCOPUS:34249021709
VL - 43
SP - 2770
EP - 2775
JO - IEEE Transactions on Magnetics
JF - IEEE Transactions on Magnetics
SN - 0018-9464
IS - 6
ER -
ID: 51234948