Origin of Giant Magnetoresistance: Bulk or Interface Scattering

Zahn, Peter; Binder, J.; Mertig, Ingrid; Zeller, R.; Dederichs, P. H.

doi:10.1103/physrevlett.80.4309

Cited by 109 publications

(69 citation statements)

References 24 publications

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“…In calculations by Zahn et al [44] on CoCu MML, the enhancement of N(E F ) at the interfaces is the consequence of the periodic potential of the layered structure that affects the electron states. This enhancement is essentially due to minority electrons of Co that are confined in the Co layer due to the mismatch of their band structure and that of Cu.…”

Section: Resultsmentioning

confidence: 99%

Enhancement of the electronic contribution to the low-temperature specific heat of an Fe/Cr magnetic multilayer

et al. 2002

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We measured the low temperature specific heat of a sputtered (F e 23Å /Cr 12Å ) 33 magnetic multilayer, as well as separate 1000Å thick Fe and Cr films. Magnetoresistance and magnetization measurements on the multilayer demonstrated antiparallel coupling between the Fe layers. Using microcalorimeters made in our group, we measured the specific heat for 4 < T < 30 K and in magnetic fields up to 8 T for the multilayer. The low temperature electronic specific heat coefficient of the multilayer in the temperature range 4 < T < 14 K is γ M L = 8.4 mJ/K 2 g − at. This is significantly larger than that measured for the Fe or Cr films (5.4 and. 3.5 mJ/K 2 mol respectively). No magnetic field dependence of γ M L was observed up to 8 T .These results can be explained by a softening of the phonon modes observed in the same data and the presence of an Fe-Cr alloy phase at the interfaces.75.70 (magnetic multilayer), 75.40 (specific heat of magnetic materials) Typeset using REVT E X 1

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Section: Resultsmentioning

confidence: 99%

Enhancement of the electronic contribution to the low-temperature specific heat of an Fe/Cr magnetic multilayer

et al. 2002

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“…32 Details on this projection technique are published elsewhere. 4 The relaxation time for Sb 2 Te 3 was fitted to experimental data and chosen constant with absolute value τ = 12 fs with respect to wave vector k k k and energy on the scale of k B T .…”

Section: Methodsmentioning

confidence: 99%

Impact of the Topological Surface State on the Thermoelectric Transport in Sb₂Te₃ Thin Films

et al. 2015

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Ab initio electronic structure calculations based on density functional theory and tight-binding methods for the thermoelectric properties of ptype Sb 2 Te 3 films are presented. The thicknessdependent electrical conductivity and the thermopower are computed in the diffusive limit of transport based on the Boltzmann equation. Contributions of the bulk and the surface to the transport coefficients are separated which enables to identify a clear impact of the topological surface state on the thermoelectric properties. By tuning the charge carrier concentration, a crossover between a surface-state-dominant and a FuchsSondheimer transport regime is achieved. The calculations are corroborated by thermoelectric transport measurements on Sb 2 Te 3 films grown by atomic layer deposition.Almost all proposed three-dimensional (3D) Z 2 topological insulators (TIs) 1,2 are efficient thermoelectric materials. That is not by coincidence, since the link between an efficient thermoelectric * To whom correspondence should be addressed † Institute of Physics, Martin Luther University HalleWittenberg, D-06099 Halle, Germany ‡ Institute of Nanostructure and Solid State Physics, Universität Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany ¶ Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany material and the topological character is the inverted band gap. 3,4 The last is due to spin-orbit coupling which switches parity of the bands and leads, if strong enough, to narrow band gaps which are favourable for efficient room-temperature thermoelectrics. Usually strong spin-orbit coupling is mediated by heavy elements which in turn also tend to reduce the material's lattice thermal conductivity, another requirement for desirable thermoelectrics.In the early 90's, Hicks and Dresselhaus 5,6 proposed the concept of low-dimensionality to increase further the thermoelectric efficiency; primarily in thin films, the thermopower S should be enlarged. However, in contrast to previous theoretical model calculations, 7,8 decreased values of S were found experimentally 9-11 for Bi 2 Te 3 and Sb 2 Te 3 thin films and were recently corroborated by both model 12,13 and ab initio calculations 4 of our groups.Thus, to resolve this discrepancy, the potential impact of the surface state (SS) of TIs on thermoelectricity needs to be investigated in more detail. In this Letter, we present ab initio calculations and transport measurements of the thermoelectric properties of Sb 2 Te 3 films at varying thickness, temperature and charge carrier concentration. (1/ cm)(g) Theoretical resultsIn the following, we discuss the doping-and temperature-dependent electrical conductivity and thermopower, as shown in Fig. 1, exemplary for a Sb 2 Te 3 film thickness of 18 quintuple-layer (QL), i.e. about 18 nm. A discussion of films with other thicknesses is given in the supplemental material. 14 The converged electronic structure results serve as input to obtain the thermoelectric transport properties at temperature T and fixed extri...

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“…10 For ballistic transport there exist methods based, for example, on lowenergy electron diffraction ͑LEED͒ 11,12 and layer KKR 13 or similar layer-type 14 techniques, on the tight-binding approach, [15][16][17] and on the transfer matrix concept; 18,19 these mostly combine the Landauer-Büttiker approach 20,21 with electronic structure methods, as will be done in the present paper. Moreover, due to potential applications in GMR and TMR devices, spin-dependent transport has come to the center of interest with an emphasis on conduction in magnetic multilayers 2,5,9,15,[22][23][24][25] and ferromagnet-semiconductor hybrides. 13,16,26 -31 In these systems the electronic spin degrees of freedom are accounted for in order to achieve spindependent resistance.…”

Section: Introductionmentioning

confidence: 99%

Korringa-Kohn-Rostoker Green-function formalism for ballistic transport

2004

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We develop a method for the calculation of ballistic transport from first principles. The multiple scattering screened Korringa-Kohn-Rostoker ͑KKR͒ method is combined with a Green-function formulation of the Landauer approach for the ballistic transport. We obtain an efficient O(N) algorithm for the calculation of ballistic conductance through a scattering region connected to semi-infinite crystalline leads. In particular we generalize the results of Baranger and Stone in the case of Bloch wave boundary conditions and we discuss relevant properties of the S matrix. We consider the implications on the application of the formalism in conjunction with a cellular multiple scattering description of the electronic structure, and demonstrate the convergence properties concerning the angular momentum expansions.

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Origin of Giant Magnetoresistance: Bulk or Interface Scattering

Cited by 109 publications

References 24 publications

Enhancement of the electronic contribution to the low-temperature specific heat of an Fe/Cr magnetic multilayer

Enhancement of the electronic contribution to the low-temperature specific heat of an Fe/Cr magnetic multilayer

Impact of the Topological Surface State on the Thermoelectric Transport in Sb₂Te₃ Thin Films

Korringa-Kohn-Rostoker Green-function formalism for ballistic transport

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Origin of Giant Magnetoresistance: Bulk or Interface Scattering

Cited by 109 publications

References 24 publications

Enhancement of the electronic contribution to the low-temperature specific heat of an Fe/Cr magnetic multilayer

Enhancement of the electronic contribution to the low-temperature specific heat of an Fe/Cr magnetic multilayer

Impact of the Topological Surface State on the Thermoelectric Transport in Sb2Te3 Thin Films

Korringa-Kohn-Rostoker Green-function formalism for ballistic transport

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Impact of the Topological Surface State on the Thermoelectric Transport in Sb₂Te₃ Thin Films