Effect of interface bonding on spin-dependent tunneling from the oxidized Co surface

Belashchenko, Kirill D.; Tsymbal, Evgeny Y.; Schilfgaarde, Mark van; Stewart, Derek A.; Oleynik, Ivan; Jaswal, S. S.

doi:10.1103/physrevb.69.174408

Cited by 88 publications

(75 citation statements)

References 29 publications

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“…͑21͒ which is controlled by the interface transmission function. 39 For ferroelectric polarization pointing right the effective barrier height and thus value of at the interface is relatively high making the P sp positive 40 whereas for ferroelectric polarization pointing left the effective barrier and thus value of at the interface are low making the P sp polarization negative. For large ⌬, however, the spin polarization becomes positive ͑due to k ↓ k ↑ tending to zero͒ independent of the ferroelectric state.…”

Section: Tunneling Conductancementioning

confidence: 99%

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Effect of spin-dependent screening on tunneling electroresistance and tunneling magnetoresistance in multiferroic tunnel junctions

2010

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Zhuravlev, M. Ye.; Maekawa, S.; and Tsymbal, Evgeny Y., "Effect of spin-dependent screening on tunneling electroresistance and tunneling magnetoresistance in multiferroic tunnel junctions" (2010 Using a ferroelectric barrier as a functional material in a ͑magnetic͒ tunnel junction has recently attracted significant interest due to new functionalities not available in conventional tunnel junctions. Switching a ferroelectric polarization of the barrier alters conductance resulting in a tunneling electroresistance ͑TER͒ effect. Using a ferroelectric barrier in a magnetic tunnel junction makes it mutiferroic where TER coexists with tunneling magnetoresistance ͑TMR͒. Here we develop a simple model for a multiferroic tunnel junction ͑MFTJ͒ which consists of two ferromagnetic electrodes separated by a ferroelectric barrier layer. The model explicitly includes the spin-dependent screening potential and thus extends previously developed models for FTJs and MFTJs. Our results demonstrate that the effect of spin-dependent screening may be sizable and may provide significant contributions to TMR and TER in MFTJs. We find that, similar to FTJs with a composite ͑ferroelectric/dielectric͒ barrier layer, the TER in a MFTJ with such a barrier is dramatically enhanced indicating that the resistance ratio between the states corresponding to the opposite polarization orientations may be as high as 10 4 and even higher. Our results demonstrate the possibility of four resistance states in MFTJs with a pronounced difference in resistance and a possibility to control these resistance by an electric field ͑through ferroelectric polarization of the barrier͒ and by a magnetic field ͑through magnetization configuration of the electrodes͒. These functionalities may be interesting to device applications of MFTJs.

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Section: Tunneling Conductancementioning

confidence: 99%

“…3͑c͔͒. Since the TMR can be considered as a product of the two transmission functions at the right and left interfaces, 39 it is expected that TMR should have similar behavior but opposite sign to that seen for the spin polarization in the inset of Fig. 3͑c͒.…”

Section: Ter and Tmr Effects In Mftjsmentioning

confidence: 99%

Effect of spin-dependent screening on tunneling electroresistance and tunneling magnetoresistance in multiferroic tunnel junctions

2010

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“…This effect was demonstrated in KNbO 3 FE films placed between SrRuO 3 or Pt electrodes [160], as well as BaTiO 3 with SrRuO 3 [161,162], Fe [116] and Pt [163] electrodes. First-principles transport calculations for Pt/BaTiO 3 /Pt FTJs show that the interface transmission function [164] of the Pt/BaTiO 3 interface differs by a factor of three depending on the polarization direction [159].…”

Section: (A) Ferroelectric Tunnel Junctionsmentioning

confidence: 99%

Multi-ferroic and magnetoelectric materials and interfaces

Velev

Jaswal

Tsymbal

2011

Phil. Trans. R. Soc. A.

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208

144

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The existence of multiple ferroic orders in the same material and the coupling between them have been known for decades. However, these phenomena have mostly remained the theoretical domain owing to the fact that in single-phase materials such couplings are rare and weak. This situation has changed dramatically recently for at least two reasons: first, advances in materials fabrication have made it possible to manufacture these materials in structures of lower dimensionality, such as thin films or wires, or in compound structures such as laminates and epitaxial-layered heterostructures. In these designed materials, new degrees of freedom are accessible in which the coupling between ferroic orders can be greatly enhanced. Second, the miniaturization trend in conventional electronics is approaching the limits beyond which the reduction of the electronic element is becoming more and more difficult. One way to continue the current trends in computer power and storage increase, without further size reduction, is to use multi-functional materials that would enable new device capabilities. Here, we review the field of multi-ferroic (MF) and magnetoelectric (ME) materials, putting the emphasis on electronic effects at ME interfaces and MF tunnel junctions.

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“…III, we discuss SDT from oxidized Co surfaces through vacuum. 19 We demonstrate that one monolayer of oxygen placed on the fcc Co͑111͒ surface creates a spin-filter effect due to the Co-O bonding. This reverses the sign of the SP from negative for the clean Co surface to positive for the oxidized Co surface.…”

Section: Introductionmentioning

confidence: 99%

Role of interface bonding in spin-dependent tunneling (invited)

Tsymbal¹,

Belashchenko²

2005

Journal of Applied Physics

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Measured positive values of the spin polarization of the tunneling current from 3d ferromagnetic metals are commonly explained by the dominant s-electron contribution based on symmetry considerations for bulk materials, ignoring the influence of the interfaces. In this work, three different models are considered which suggest that the spin polarization is primarily determined by the electronic and atomic structures of the ferromagnet/insulator interfaces rather than by the bulk properties. A simple tight-binding model demonstrates that the existence of interface states and their contribution to the tunneling current depend on the degree of hybridization between the orbitals on metal and insulator atoms. The decisive role of the interface bonding is further supported by considering spin-dependent tunneling from oxidized Co surfaces through vacuum and in Co/ Al 2 O 3 / Co tunnel junctions within the first-principles Green's-function approach. For the oxidized Co surface it is found that the Co-O bonding at the surface removes the conducting orbitals forming the bulk Bloch states from the Fermi level, creating an additional tunneling barrier for minority-spin electrons. For the Co/ Al 2 O 3 / Co junctions, two types of the interface O atoms are distinguished: those which saturate Al bonds and those which are adsorbed by Co. The latter bind strongly to Co creating interface states which enhance the tunneling current in the majority-spin channel. In both cases, the spin polarization changes sign and becomes positive, evidencing the crucial role of the interface structure and bonding.

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Effect of interface bonding on spin-dependent tunneling from the oxidized Co surface

Cited by 88 publications

References 29 publications

Effect of spin-dependent screening on tunneling electroresistance and tunneling magnetoresistance in multiferroic tunnel junctions

Effect of spin-dependent screening on tunneling electroresistance and tunneling magnetoresistance in multiferroic tunnel junctions

Multi-ferroic and magnetoelectric materials and interfaces

Role of interface bonding in spin-dependent tunneling (invited)

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