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.

Effect of temperature on the thermodynamic density of states in a quantizing magnetic field

2014 ◽  
Vol 48 (10) ◽  
pp. 1287-1292 ◽  
Author(s):  
G. Gulyamov ◽  
U. I. Erkaboev ◽  
N. Yu. Sharibaev
Keyword(s):  
Magnetic Field ◽  
Density Of States ◽  
Effect Of Temperature ◽  
Quantizing Magnetic Field

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.

About the Metal-Insulator Transition in Quasicrystals

2000 ◽  
Vol 643 ◽  
Author(s):  
J. Delahaye ◽  
C. Berger ◽  
T. Grenet ◽  
G. Fourcaudot
Keyword(s):  
Magnetic Field ◽  
Fermi Level ◽  
Electronic Properties ◽  
Field Dependence ◽  
Density Of States ◽  
Disordered Systems ◽  
Magnetic Field Dependence ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Mi Transition

AbstractElectronic properties (conductivity and density of states) of quasicrystals present strong similarities with disordered semiconductor based systems on both sides of the Mott-Anderson metal-insulator (MI) transition. We revisit the conductivity of the i-AlCuFe and i-AlPdMn phases, which has temperature and magnetic field dependence characteristic of the metallic side of the transition. The i-AlPdRe ribbon samples can be on either side of the transition depending on their conductivity value. In all these i-phases, the density of states at the Fermi level EF is low. Its energy dependence close to EF is similar to disordered systems close to the MI transition where it is ascribed to effects of interactions between electrons and disorder.

Quantum variation of Fermi level in bismuth at high magnetic field

1968 ◽  
Vol 26 (5) ◽  
pp. 187-188 ◽  
Author(s):  
S. Takano ◽  
H. Kawamura
Keyword(s):  
Magnetic Field ◽  
Fermi Level ◽  
High Magnetic Field

Structural and Magnetic Study on the Effect of Substitution of Cobalt by d-Valent Elements of Co2FeSi Heusler Alloy

2016 ◽  
Vol 708 ◽  
pp. 37-41
Author(s):  
Muhammad Noor Syazwan Saimin ◽  
Siti Sumaiyah Sheikh Abdul Aziz ◽  
A.M.M. Ali ◽  
Oskar Hasdinor Hassan ◽  
Muhd Zu Azhan Yahya ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Electronic Structure ◽  
Band Structure ◽  
Fermi Level ◽  
Density Of States ◽  
Magnetic Moment ◽  
Local Magnetic Moment ◽  
Half Metallic ◽  
New States ◽  
Full Heusler

In this paper, the effect of substitution of Co by d-valent elements such as Ag and Pt on electronic structure and magnetic properties of full Heusler type Co2FeSi alloys was investigated. Structural study reveals the presence of a small gap in the minority band structure around the vicinity of the Fermi level on Co2FeSi resulting to half-metallic behaviour. However, CoFeSiAg and CoFeSiPt cannot preserved the half-metalicity due to disappearing of the gap in the minority band structure due to the creation of new states around the Fermi level in the minority density of states. The variation in the magnetic moment of Co2FeSi with change of the atoms was attributed to the change in the local magnetic moment of atoms.

Magnetic field and temperature dependences of the electrical resistance of onion structure carbon

2010 ◽  
Vol 3 (2) ◽  
pp. 95-98
Author(s):  
Evgeny N. Tkachev ◽  
Anatoliy I. Romanenko ◽  
Olga B. Anikeeva ◽  
Timofey I. Buryakov ◽  
Kamil R. Zhdanov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Physical Properties ◽  
Fermi Level ◽  
Density Of States ◽  
Electrical Resistance ◽  
Variable Range Hopping ◽  
Hopping Conductivity ◽  
Variable Range ◽  
Localization Radius ◽  
Temperature Dependences

In this paper electro physical properties of samples of onion-like carbon have been investigated. Samples have been synthesized by method of thermal graphitization of nanodiamonds. 1D Mott variable-range hopping conductivity has been observed for temperature dependences of resistance of nanoonions volume samples at temperature range 4.2 K – 300 K. Also second-degree increase of positive magnetoresistance up to 6 tesla has been revealed. Some coefficients such as localization radius a, density of states on Fermi level N(EF) have been estimated.

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