scholarly journals Sign reversal of spin polarization inCo/Ru/Al2O3/Comagnetic tunnel junctions

2001 ◽  
Vol 64 (10) ◽  
Author(s):  
P. LeClair ◽  
B. Hoex ◽  
H. Wieldraaijer ◽  
J. T. Kohlhepp ◽  
H. J. M. Swagten ◽  
...  
Keyword(s):  
Spin Polarization ◽  
Tunnel Junctions ◽  
Sign Reversal

scholarly journals THE IMPORTANCE OF Fe SURFACE STATES FOR MAGNETIC TUNNEL JUNCTION BASED SPINTRONIC DEVICES

2008 ◽  
Vol 22 (26) ◽  
pp. 2529-2551 ◽  
Author(s):  
ATHANASIOS N. CHANTIS ◽  
KIRILL D. BELASHCHENKO ◽  
EVGENY Y. TSYMBAL ◽  
INNA V. SUS
Keyword(s):  
Spin Polarization ◽  
Tunnel Junctions ◽  
Strong Dependence ◽  
Magnetic Tunnel Junctions ◽  
Interface States ◽  
Tunneling Magnetoresistance ◽  
Sign Reversal ◽  
Spintronic Devices ◽  
Spin Electronics ◽  
Minority Spin

In this article we give a review of our recent theoretical studies of the influence of Fe (001) surface (interface) states on spin-polarized electron transport across magnetic tunnel junctions with Fe electrodes. We show that minority-spin surface (interface) states are responsible for at least two effects which are important for spin electronics. First, they can produce a sizable tunneling anisotropic magnetoresistance in magnetic tunnel junctions with a single Fe electrode. The effect is driven by a Rashba shift of the resonant surface band when the magnetization changes direction. This can introduce a new class of spintronic devices, namely, tunneling magnetoresistance junctions with a single ferromagnetic electrode. Second, in Fe/GaAs (001) magnetic tunnel junctions minority-spin interface states produce a strong dependence of the tunneling current spin polarization on applied electrical bias. A dramatic sign reversal within a voltage range of just a few tenths of an eV is predicted. This explains the observed sign reversal of spin polarization in recent experiments of electrical spin injection in Fe/GaAs (001) and related reversal of tunneling magnetoresistance through vertical Fe/GaAs/Fe trilayers.

scholarly journals Magneto-ionic control of spin polarization in multiferroic tunnel junctions

2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Yingfen Wei ◽  
Sylvia Matzen ◽  
Cynthia P. Quinteros ◽  
Thomas Maroutian ◽  
Guillaume Agnus ◽  
...  
Keyword(s):  
Electric Field ◽  
Spin Polarization ◽  
Tunnel Junctions ◽  
Tunnel Barrier ◽  
Magnetoresistance Effect ◽  
Sign Reversal ◽  
Electrical Control ◽  
Ionic Effect ◽  
Field Cycling ◽  
Number Of Cycles

AbstractMultiferroic tunnel junctions (MFTJs) with Hf0.5Zr0.5O2 barriers are reported to show both tunneling magnetoresistance effect (TMR) and tunneling electroresistance effect (TER), displaying four resistance states by magnetic and electric field switching. Here we show that, under electric field cycling of large enough magnitude, the TER can reach values as large as 106%. Moreover, concomitant with this TER enhancement, the devices develop electrical control of spin polarization, with sign reversal of the TMR effect. Currently, this intermediate state exists for a limited number of cycles and understanding the origin of these phenomena is key to improve its stability. The experiments presented here point to the magneto-ionic effect as the origin of the large TER and strong magneto-electric coupling, showing that ferroelectric polarization switching of the tunnel barrier is not the main contribution.

Magnetism and Spin Tunneling in Nanostructures

1997 ◽  
Vol 491 ◽  
Author(s):  
Alexander Bratkovsky
Keyword(s):  
Spin Polarization ◽  
Tunnel Junctions ◽  
Iron Group ◽  
Defect States ◽  
Resistance Change ◽  
Half Metallic ◽  
Spin Tunneling ◽  
Inelastic Tunneling ◽  
Resonant Tunnel ◽  
General Method

ABSTRACTIn the present paper different tunneling mechanisms in conventional and half-metallic ferromagnetic tunnel junctions are analyzed within the same general method. Theoretically calculated direct tunneling in iron group systems leads to about a 30% change in resistance, which is close but lower than experimentally observed values. It is shown that the larger observed values of the TMR might be a result of tunneling involving surface polarized states. We find that tunneling via resonant defect states in the barrier radically decreases the TMR (down to 4% with Fe-based electrodes), and a resonant tunnel diode structure would give a TMR of about 8%. With regards to inelastic tunneling, magnons and phonons exhibit opposite effects: one-magnon emission generally results in spin mixing and, consequently, reduces the TMR, whereas phonons are shown to enhance the TMR. The inclusion of both magnons and phonons reasonably explains an unusual bias dependence of the TMR.The model presented here is applied qualitatively to half-metallics with 100% spin polarization, where one-magnon processes are suppressed and the change in resistance in the absence of spin-mixing on impurities may be arbitrarily large. Even in the case of imperfect magnetic configurations, the resistance change can be a few 1000 percent. Examples of half-metallic systems are CrO2/TiO2 and CrO2/RuO2, and an account of their peculiar band structures is presented. The implications and relation of these systems to CMR materials, which are nearly half-metallic, are discussed.

Role of Metal-Oxide Interface in Determining the Spin Polarization of Magnetic Tunnel Junctions

Science ◽  
1999 ◽  
Vol 286 (5439) ◽  
pp. 507-509 ◽  
Author(s):  
Jose Maria De Teresa ◽  
Agnès Barthélémy ◽  
Albert Fert ◽  
Jean Pierre Contour ◽  
François Montaigne ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Metal Oxide ◽  
Spin Polarization ◽  
Tunnel Junctions ◽  
Magnetic Tunnel Junctions ◽  
Ferromagnetic Transition ◽  
Oxide Interface ◽  
Oxide Interfaces ◽  
Structure Of Metal

The role of the metal-oxide interface in determining the spin polarization of electrons tunneling from or into ferromagnetic transition metals in magnetic tunnel junctions is reported. The spin polarization of cobalt in tunnel junctions with an alumina barrier is positive, but it is negative when the barrier is strontium titanate or cerium lanthanite. The results are ascribed to bonding effects at the transition metal–barrier interface. The influence of the electronic structure of metal-oxide interfaces on the spin polarization raises interesting fundamental problems and opens new ways to optimize the magnetoresistance of tunnel junctions.

Quenching of Spin Polarization Switching in Organic Multiferroic Tunnel Junctions by Ferroelectric “Ailing-Channel” in Organic Barrier

2018 ◽  
Vol 10 (36) ◽  
pp. 30614-30622 ◽  
Author(s):  
Shiheng Liang ◽  
Zhongwei Yu ◽  
Xavier Devaux ◽  
Anthony Ferri ◽  
Weichuan Huang ◽  
...  
Keyword(s):  
Spin Polarization ◽  
Tunnel Junctions ◽  
Polarization Switching

Magnetoresistance and spin polarization of electron current in magnetic tunnel junctions

2007 ◽  
Vol 75 (17) ◽  
Author(s):  
N. N. Beletskii ◽  
G. P. Berman ◽  
A. R. Bishop ◽  
S. A. Borysenko ◽  
V. M. Yakovenko
Keyword(s):  
Spin Polarization ◽  
Tunnel Junctions ◽  
Magnetic Tunnel Junctions ◽  
Electron Current

How Many Fe layers Cause TMR?

2006 ◽  
Vol 941 ◽  
Author(s):  
Christian Heiliger ◽  
Peter Zahn ◽  
Ingrid Mertig
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Structural Properties ◽  
Spin Polarization ◽  
Tunnel Junction ◽  
Tunnel Junctions ◽  
Tunneling Current ◽  
Electronic Structure Calculations ◽  
High Spin Polarization ◽  
Structure Calculations

ABSTRACTThe influence of the structural properties of the leads of planar tunnel junctions on the tunneling current is investigated by means of ab initio electronic structure calculations. In particular, a NM/Fe/MgO/Fe/NM tunnel junction with non-magnetic (NM) leads and finite Fe spacer layers between the leads and the MgO barrier is discussed. The conductance is calculated as a function of the number of Fe layers. The results show that even one iron layer next to the barrier is sufficient to obtain a high spin polarization and a high TMR ratio. This finding implies that similar results can be expected for tunnel junctions with nonmagnetic and even amorphous leads, if states of Δ1 symmetry are provided.

Inverse Magnetoresistance In Manganite/SrTiO3/Co Tunnel Junctions

1999 ◽  
Vol 574 ◽  
Author(s):  
J. M. De Teresa ◽  
A. Barthélémy ◽  
J. P. Contour ◽  
A. Fert ◽  
R. Lyonnet ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Fermi Level ◽  
Spin Polarization ◽  
Density Of States ◽  
High Magnetic Field ◽  
Applied Voltage ◽  
Tunnel Junctions ◽  
Effect Of Temperature ◽  
Half Metallic ◽  
Tunnel Magnetoresistance

AbstractIn La0.7Sr0.3MnO3/SrTiO3/Co tunnel junctions, the half-metallic nature of La0.7Sr0.3MnO3 allows probing the spin polarization of Co. For applied voltage bias around zero volts, an inverse tunnel magnetoresistance is found, indicating the negative spin polarization of Co at the Fermi level as expected from the density of states of the “d” band in Co. The bias dependence of the magnetoresistance reflects the structure of the “d” band density of states of Co. In this article we underline the important consequences for the knowledge of the spin-dependent tunneling in solids brought by these results and describe in detail the effect of temperature and high magnetic field on the magnetoresistance.

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