skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Tunneling magnetoresistance and electroresistance in Fe/PbTiO{sub 3}/Fe multiferroic tunnel junctions

Abstract

We perform first-principles electronic structure and spin-dependent transport calculations for a Fe/PbTiO{sub 3}/Fe multiferroic tunnel junction with asymmetric TiO{sub 2}- and PbO-terminated interfaces. We demonstrate that the interfacial electronic reconstruction driven by the in situ screening of ferroelectric polarization, in conjunction with the intricate complex band structure of barrier, play a decisive role in controlling the spin-dependent tunneling. Reversal of ferroelectric polarization results in a transition from insulating to half-metal-like conducting state for the interfacial Pb 6p{sub z} orbitals, which acts as an atomic-scale spin-valve by releasing the tunneling current in antiparallel magnetization configuration as the ferroelectric polarization pointing to the PbO-terminated interface. This effect produces large change in tunneling conductance. Our results open an attractive avenue in designing multiferroic tunnel junctions with excellent performance by exploiting the interfacial electronic reconstruction originated from the in situ screening of ferroelectric polarization.

Authors:
 [1]
  1. School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)
Publication Date:
OSTI Identifier:
22598901
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 120; Journal Issue: 7; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ASYMMETRY; ELECTRONIC STRUCTURE; FERROELECTRIC MATERIALS; INTERFACES; LEAD OXIDES; MAGNETIZATION; MAGNETORESISTANCE; METALS; POLARIZATION; SCREENING; SPIN; TITANATES; TITANIUM OXIDES; TUNNEL EFFECT; TUNNEL JUNCTIONS; VALVES

Citation Formats

Dai, Jian-Qing, E-mail: djqkust@sina.com. Tunneling magnetoresistance and electroresistance in Fe/PbTiO{sub 3}/Fe multiferroic tunnel junctions. United States: N. p., 2016. Web. doi:10.1063/1.4960695.
Dai, Jian-Qing, E-mail: djqkust@sina.com. Tunneling magnetoresistance and electroresistance in Fe/PbTiO{sub 3}/Fe multiferroic tunnel junctions. United States. doi:10.1063/1.4960695.
Dai, Jian-Qing, E-mail: djqkust@sina.com. 2016. "Tunneling magnetoresistance and electroresistance in Fe/PbTiO{sub 3}/Fe multiferroic tunnel junctions". United States. doi:10.1063/1.4960695.
@article{osti_22598901,
title = {Tunneling magnetoresistance and electroresistance in Fe/PbTiO{sub 3}/Fe multiferroic tunnel junctions},
author = {Dai, Jian-Qing, E-mail: djqkust@sina.com},
abstractNote = {We perform first-principles electronic structure and spin-dependent transport calculations for a Fe/PbTiO{sub 3}/Fe multiferroic tunnel junction with asymmetric TiO{sub 2}- and PbO-terminated interfaces. We demonstrate that the interfacial electronic reconstruction driven by the in situ screening of ferroelectric polarization, in conjunction with the intricate complex band structure of barrier, play a decisive role in controlling the spin-dependent tunneling. Reversal of ferroelectric polarization results in a transition from insulating to half-metal-like conducting state for the interfacial Pb 6p{sub z} orbitals, which acts as an atomic-scale spin-valve by releasing the tunneling current in antiparallel magnetization configuration as the ferroelectric polarization pointing to the PbO-terminated interface. This effect produces large change in tunneling conductance. Our results open an attractive avenue in designing multiferroic tunnel junctions with excellent performance by exploiting the interfacial electronic reconstruction originated from the in situ screening of ferroelectric polarization.},
doi = {10.1063/1.4960695},
journal = {Journal of Applied Physics},
number = 7,
volume = 120,
place = {United States},
year = 2016,
month = 8
}
  • We report the investigation on the ferroelectricity and tunneling electroresistance (TER) effect in PbTiO{sub 3} (PTO)-based ferroelectric tunnel junctions (FTJs) using first-principles calculations. For symmetric FTJs, we have calculated the average polarizations of PTO film and effective screening lengths of different metal electrodes for a number of FTJs, which is useful for experimental research. For asymmetric FTJs, significant asymmetric ferroelectric displacements in PTO film are observed, which is attributed to the intrinsic field generated by the two dissimilar electrodes. Moreover, by performing quantum transport calculations on those asymmetric FTJs, a sizable TER effect is observed. It is found that themore » asymmetry of ferroelectric displacements in PTO barrier, which is determined by the difference of work functions of the electrodes, controls the observed TER effect. Our results will help unravel the TER mechanism of asymmetric FTJs in most experiments and will be useful for the designing of FTJ-based devices.« less
  • The effect of annealing on the changes in the inelastic tunneling contributions in tunneling conductance of ion beam sputtered CoFe/MgO/NiFe magnetic tunnel junctions (MTJs) is investigated. The inelastic contributions are evaluated using hopping conduction model of Glazman and Matveev in the temperature range of 25–300 K. The hopping through number of series of localized states present in the barrier due to structural defects increases from 9 (in as deposited MTJ) to 18 after annealing (at 200 °C/1 h); although no changes in the interface roughness of CoFe-MgO and MgO-NiFe interfaces are observed as revealed by the x-ray reflectance studies on planar MTJs. Themore » bias dependence of tunneling magnetoresistance (TMR) at 25 K is found to get improved after annealing as revealed by the value V{sub 1/2} (the bias value at which the TMR reaches to half of its value at nearly zero bias); which is 78 mV (in MTJ annealed at 200 °C/1 h) 2.5 times the value of 33 mV (in as deposited MTJ). At 25 K the inelastic tunneling spectra revealed the presence of zero bias anomaly and magnon excitations in the range of 10–15 mV. While the barrier height exhibited a strong temperature dependence with nearly 100% increase from the value at 300 K to 25 K, the temperature dependence of TMR becomes steep after annealing.« less
  • Spin tunnel junctions fabricated with one interposed Fe{endash}FeOx layer between the Al{sub 2}O{sub 3} barrier and the top CoFe pinned electrode show large tunneling magnetoresistance (TMR) (40%) for anneals up to 380{degree}C. The annealing temperature T{sub TMR}{sup *}, where maximum TMR occurs, increases with the inserted Fe{endash}FeOx layer thickness. For samples with thicker inserted layer, the pinned layer moment (which usually starts to decay below 300{degree}C in the normal junctions) increases with annealing temperature up to 380{degree}C and remains at a maximum until 450{degree}C. The large TMR at high temperature is related with the diffusion of extra Fe (from themore » Fe{endash}FeOx layer) into the electrode interfacial region and the as-deposited paramagnetic FeOx decomposition into metallic Fe, and possibly the formation of some Fe{sub 3}O{sub 4}, which compensate the interface polarization loss associated with Mn interdiffusion. Rutherford backscattering spectrometry analysis confirms partial Fe diffusion into the top CoFe electrode after anneal. Meanwhile, x-ray photoelectron spectra for the Fe2p core level show that the FeOx contribution in the upper part of the inserted layer decreases upon annealing, while it increases in the inner part near the barrier, suggesting the FeOx decomposition and the oxygen diffusion toward the inner metallic Fe and Al barrier. The study of R{times}A values and barrier parameters versus annealing temperature for samples with 7 and 25 Aa Fe{endash}FeOx also reflects the above structural changes in the inserted layer. {copyright} 2001 American Institute of Physics.« less
  • We have observed very large tunneling magnetoresistance (TMR) in Ga{sub 1{minus}x}Mn{sub x}As/AlAs/Ga{sub 1{minus}x}Mn{sub x}As ferromagnetic semiconductor tunnel junctions. A TMR ratio as high as 75% was obtained in a junction with a thin (1.5 nm) AlAs tunnel barrier when the magnetic field was applied along the [100] axis in the film plane. The TMR ratio decreased when the applied magnetic field direction was along the [1{bar 1}0] and [110]. This anisotropic TMR was found to be explained by the single-domain theory assuming cubic magnetic anisotropy with the easy axis of {l_angle}100{r_angle}, which is induced by the zincblende-type Ga{sub 1{minus}x}Mn{sub x}Asmore » crystal structure. {copyright} 2001 American Institute of Physics.« less