Influence of the interface structure on the bias dependence of tunneling magnetoresistance

Heiliger, Christian; Zahn, Peter; Yavorsky, B. Yu.; Mertig, Ingrid

doi:10.1103/physrevb.72.180406

Cited by 83 publications

(90 citation statements)

References 32 publications

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“…Since structural information of Fe/MgO/Fe MTJs with embedded ultrathin Cr and Co spacers are not reported so far, we resort to a geometry of planar Fe(001)/MgO/Fe(001) junctions which has been determined experimentally by surface x-ray diffraction analyses 30,31 . This structure has been used in previous theoretical studies 16,32 . In detail, a supercell geometry with six MgO layers sandwiched by 20 Fe layers was used to compute self-consistently the atomic potentials.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Tailoring tunnel magnetoresistance by ultrathin Cr and Co interlayers: A first-principles investigation of Fe/MgO/Fe junctions

et al. 2010

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We report on systematic ab-initio investigations of Co and Cr interlayers embedded in Fe(001)/MgO/Fe(001) magnetic tunnel junctions, focusing on the changes of the electronic structure and the transport properties with interlayer thickness. The results of spin-dependent ballistic transport calculations reveal options to specifically manipulate the tunnel magnetoresistance ratio. The resistance area products and the tunnel magnetoresistance ratios show a monotonous trend with distinct oscillations as a function of the Cr thickness. These modulations are directly addressed and interpreted by means of magnetic structures in the Cr films and by complex band structure effects. The characteristics for embedded Co interlayers are considerably influenced by interface resonances which are analyzed by the local electronic structure.

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Section: Theoretical Backgroundmentioning

confidence: 99%

Tailoring tunnel magnetoresistance by ultrathin Cr and Co interlayers: A first-principles investigation of Fe/MgO/Fe junctions

et al. 2010

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“…[9][10][11][12][13][14] Several mechanisms have been proposed to explain this behavior, including inelastic spinflip scattering processes by interfacial magnon excitations, 15,16 spin-independent two-step elastic tunneling via defect states in the insulating barrier, 17 voltage-dependent density of states at the Fermi level, 18 and the electronic structure of the FM electrodes. 12,13,19,20 While in MTJ structures the relative orientation of magnetizations affects the flow of spin-polarized current, Slonczewski 21 and Berger 22 independently predicted a reverse effect. Namely, the flow of spin-polarized current in noncollinear MTJ can transfer spin angular momentum from the carriers to the ferromagnet and alter the orientation of the corresponding magnetization at sufficiently high current density, even in the absence of an applied field.…”

Section: Introductionmentioning

confidence: 99%

Spin-transfer torque in magnetic tunnel junctions

et al. 2009

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We present a theoretical study of the spin-transfer torque vector and the tunneling magnetoresistance ͑TMR͒ for symmetric magnetic tunnel junctions ͑MTJ͒ using the single-band tight-binding model and the nonequilibrium Keldysh formalism. We provide a comprehensive analysis of the effect of band filling and exchange splitting of the FM leads on the bias behavior of the spin-transfer component, T ʈ , in the plane containing the magnetizations of the two magnetic layers, and the fieldlike component, T Ќ , perpendicular to this plane. We demonstrate that both components of the spin torque and the TMR can exhibit a wide range of interesting and unusual bias behavior. We show that T ʈ ͑V͒ satisfies an expression involving the difference in spin currents between the ferromagnetic ͑FM͒ and antiferromagnetic ͑AF͒ configurations, which is general and independent of the details of the electronic structure. The spin current for the FM ͑AF͒ alignment is shown to have a linear ͑quadratic͒ bias dependence, whose origin lies in the symmetric ͑asymmetric͒ nature of the barrier. On the other hand, the bias dependence of T Ќ is quadratic with d 2 T Ќ / dV 2 Ͻ 0, and it can change sign at finite bias. Finally, we show that the exchange splitting and band filling have a large effect on the bias dependence of the TMR.

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“…6,18,19 Theoretical calculations claimed that the transport properties can change drastically if such an FeO layer is present at the Fe/MgO interface. 11,20,21 Several different geometries for the Fe/MgO interface have been proposed theoretically, based on relaxing ͓Fe͔ n / ͓MgO͔ m supercells, consisting of n Fe and m MgO monolayers ͑MLs͒ subject to various constraints. In Ref.…”

Section: Introductionmentioning

confidence: 99%

Effects of structural relaxation on calculations of the interface and transport properties of Fe/MgO(001) tunnel junctions

et al. 2009

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The relaxation of the interface structure of Fe/MgO͑100͒ magnetic tunnel junctions predicted by densityfunctional theory depends significantly on the choice of exchange and correlation functional. Bader analysis reveals that structures obtained by relaxing the cell with the local spin-density approximation ͑LSDA͒ display a different charge transfer than those relaxed with the generalized gradient approximation ͑GGA͒. As a consequence, the electronic transport is found to be extremely sensitive to the interface structure. In particular, the conductance for the LSDA-relaxed geometry is about 1 order of magnitude smaller than that of the GGArelaxed one. Surprisingly, the effect of the exchange and correlation potential within both the LSDA and the GGA has a little effect on the calculated transmission coefficient when applied to the same Fe/MgO/Fe ͑001͒ geometry. The high sensitivity of the electronic current to the details of the relaxed interface might explain the discrepancy between the experimental and calculated values of magnetoresistance.

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Influence of the interface structure on the bias dependence of tunneling magnetoresistance

Cited by 83 publications

References 32 publications

Tailoring tunnel magnetoresistance by ultrathin Cr and Co interlayers: A first-principles investigation of Fe/MgO/Fe junctions

Tailoring tunnel magnetoresistance by ultrathin Cr and Co interlayers: A first-principles investigation of Fe/MgO/Fe junctions

Spin-transfer torque in magnetic tunnel junctions

Effects of structural relaxation on calculations of the interface and transport properties of Fe/MgO(001) tunnel junctions

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