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R. Mattana et al.
Fig. 5.6 a Schemes illustrating electron tunnelling through an amorphous Al-O barrier (left) and
through a crystalline MgO barrier (right). b Band dispersion of bcc Fe(001) for the minority and
majority spins. 1 Bloch states are present at the Fermi level only for the majority spins. Tunnelling
DOS for Fe/MgO/Fe at k = 0 for majority c and minority d spins. Decay of 1 Bloch states in
MgO is less attenuated than the 1 Bloch states. e TMR of 600% obtained at room temperature for
a CoFeB/MgO/CoFeB MTJ. Adapted from [18] (a, b) with permission (Copyright 2007, Institute
of Physics), from [17] (c, d) with permission (Copyright 2001, American Physical Society) and
from [19] (e) with permission (Copyright 2008, American Institute of Physics Publishing)
the MgO-based tunnel junctions at the core of the development of new spintronic
devices like the MRAMs.
After these theoretical predictions, a strong research effort has been made to
obtain epitaxial growth of structures for Fe/MgO/Fe or CoFeB/MgO/CoFeB [20,
21]. These efforts have resulted in a TMR of about 600% obtained in 2009 [19] in
CoFeB/MgO/CoFeB MTJs at room temperature [see Fig. 5.6e]. An excellent review
on the physics of tunnelling transport in MgO-based systems and the experimental
state of the art for TMR has been written by S. Yuasa [18].
Since the measurements of TMR effects at room temperature in 1995, a lot of
work has been done in order to both increase the TMR ratio and reduce the MTJ
resistance. This has been achieved by developing high-quality crystalline MgO-based
MTJs. This effort has led to the development of a new class of magnetic memories
called MRAMs.
R. Mattana et al.
Fig. 5.6 a Schemes illustrating electron tunnelling through an amorphous Al-O barrier (left) and
through a crystalline MgO barrier (right). b Band dispersion of bcc Fe(001) for the minority and
majority spins. 1 Bloch states are present at the Fermi level only for the majority spins. Tunnelling
DOS for Fe/MgO/Fe at k = 0 for majority c and minority d spins. Decay of 1 Bloch states in
MgO is less attenuated than the 1 Bloch states. e TMR of 600% obtained at room temperature for
a CoFeB/MgO/CoFeB MTJ. Adapted from [18] (a, b) with permission (Copyright 2007, Institute
of Physics), from [17] (c, d) with permission (Copyright 2001, American Physical Society) and
from [19] (e) with permission (Copyright 2008, American Institute of Physics Publishing)
the MgO-based tunnel junctions at the core of the development of new spintronic
devices like the MRAMs.
After these theoretical predictions, a strong research effort has been made to
obtain epitaxial growth of structures for Fe/MgO/Fe or CoFeB/MgO/CoFeB [20,
21]. These efforts have resulted in a TMR of about 600% obtained in 2009 [19] in
CoFeB/MgO/CoFeB MTJs at room temperature [see Fig. 5.6e]. An excellent review
on the physics of tunnelling transport in MgO-based systems and the experimental
state of the art for TMR has been written by S. Yuasa [18].
Since the measurements of TMR effects at room temperature in 1995, a lot of
work has been done in order to both increase the TMR ratio and reduce the MTJ
resistance. This has been achieved by developing high-quality crystalline MgO-based
MTJs. This effort has led to the development of a new class of magnetic memories
called MRAMs.