Spin-polarized tunnelling, magnetoresistance and interfacial effects in ferromagnetic junctions

Moodera, Jagadeesh S.; Kim, Tae Kee; Tanaka, C. T.; Groot, C.H. de

doi:10.1080/13642810008208608

Cited by 40 publications

(34 citation statements)

References 57 publications

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“…The Al 2 O 3 tunnel barriers obtained by oxidation of the Al film are amorphous 8,10 . Concerning the α-Al 2 O 3 crystals, it is known from the band structure calculations 29 that the gap (which is not direct) between the upper valence band and the conduction band is of the width of ≈ 6.29 eV.…”

Section: Theoretical Modelmentioning

confidence: 99%

“…Experimentally it was observed 5,7,8 that the TMR depends critically on the material of the insulating barrier and on the conditions of its preparation, in particular on the imperfections of the interfaces between the metal and the insulating layer 9,10 . On the other hand, the first theory suggested by M. Julliere expresses the TMR ratio in terms of the effective spin polarizations P 1 and P 2 of two magnetic layers via the expression TMR = 2P 1 P 2 /(1 + P 1 P 2 ), and thus predicts no dependence of the TMR on the parameters of the barrier.…”

Section: Introductionmentioning

confidence: 99%

“…Only 20 years later, the large values of TMR at room temperature were obtained in magnetic junctions comprising the Al 2 O 3 barrier 2,3,4 . Since that time, there has been a renewed technological and fundamental interest to the tunneling phenomenon and during the last decade a lot of experimental and theoretical papers were published on this topic (see reviews [5,6,7,8]). …”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, the first theory suggested by M. Julliere expresses the TMR ratio in terms of the effective spin polarizations P 1 and P 2 of two magnetic layers via the expression TMR = 2P 1 P 2 /(1 + P 1 P 2 ), and thus predicts no dependence of the TMR on the parameters of the barrier. In spite of Julliere's formula is widely used for the interpretation of the experimental data 8 , it does not have rigorous theoretical foundation 11 . The dependence of the TMR magnitude on the parameters of the tunnel barrier and the metal/insulator interface was taken into account in the subsequent theories.…”

Section: Introductionmentioning

confidence: 99%

“…For F/O/F tunnel junctions the most successful material until now has been alumina, Al 2 O 3 8 . The Al 2 O 3 tunnel barriers are usually fabricated by the natural or plasma oxidation of the Al layer 5,8 . The subsequent structural analysis, e.g.…”

Section: Introductionmentioning

confidence: 99%

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Influence ofs−dinterfacial scattering on the magnetoresistance of magnetic tunnel junctions

Bagrets

Vedyayev

et al. 2002

Phys. Rev. B

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We propose the two-band s-d model to describe theoretically a diffuse regime of the spin-dependent electron transport in magnetic tunnel junctions (MTJ's) of the form F/O/F where F's are 3d transition metal ferromagnetic layers and O is the insulating spacer. We aim to explain the strong interface sensitivity of the tunneling properties of MTJ's and investigate the influence of electron scattering at the nonideal interfaces on the degradation of the TMR magnitude. The generalized Kubo formalism and the Green's functions method were used to calculate the conductance of the system. The vertex corrections to the conductivity were found with the use of "ladder" approximation combined with the coherent-potential approximation (CPA) that allowed to consider the case of strong electron scattering. It is shown that the Ward identity is satisfied in the framework of this approximation that provides the necessary condition for a conservation of a tunneling current. Based on the known results of ab-initio calculations of the TMR for ballistic junctions, we assume that exchange split quasi-free s-like electrons with the density of states being greater for the majority spin sub-band give the main contribution to the TMR effect. We show that, due to interfacial inter-band scattering, the TMR can be substantially reduced even down to zero value. This is related to the fact that delocalized quasi-free electrons can scatter into the strongly localized d sub-band with the density of states at the Fermi energy being larger for minority spins compared to majority spins. It is also shown that spin-flip electron scattering on the surface magnons within the interface leads to a further decrease of the TMR at finite temperature.

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Section: Theoretical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence ofs−dinterfacial scattering on the magnetoresistance of magnetic tunnel junctions

Bagrets

Vedyayev

et al. 2002

Phys. Rev. B

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Interfacial Sensitivity and Zero-Bias Anomalies in Magnetic Tunnel Junctions

LeClair

Swagten

Jonge

2002

phys. stat. sol. (a)

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Large zero-bias resistance anomalies as well as an extremely strong decrease of magnetoresistance were observed in Co/Al 2 O 3 /Co magnetic tunnel junctions with thin Cr interfacial layers. The tunnel magnetoresistance decays exponentially with nominal Cr interlayer thickness with a length scale of $ 0:1 nm. The magnetoresistance decay, as well as some aspects of the zero-bias anomalies, can be understood by considering a strong spin-dependent modification of the density of states at Co/Cr interfaces and existing models for zero-bias anomalies. The effect of the density of states modification is also observed in the transport of the metallic electrodes alone, confirming the key role of the Co/Cr interface. However, several aspects of the zero-bias anomalies cannot be explained at present, suggesting perhaps a novel form of the Kondo resonance.

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Spin-polarized tunneling

Moodera¹,

Meservey²

2004

Magnetoelectronics

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Spin-polarized tunnelling, magnetoresistance and interfacial effects in ferromagnetic junctions

Cited by 40 publications

References 57 publications

Influence ofs−dinterfacial scattering on the magnetoresistance of magnetic tunnel junctions

Influence ofs−dinterfacial scattering on the magnetoresistance of magnetic tunnel junctions

Interfacial Sensitivity and Zero-Bias Anomalies in Magnetic Tunnel Junctions

Spin-polarized tunneling

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