99 research outputs found
Magnetic Diode Effect in Double Barrier Tunnel Junctions
A quantum statistical theory of spin-dependent tunneling through asymmetric
magnetic double barrier junctions is presented which describes ballistic
and diffuse tunneling by a single analytical expression. It is evidenced that
the key parameter for the transition between these two tunneling regimes is the
electron scattering. For these junctions a strong asymmetric behaviour in the
I-V characteristics and the tunnel magnetoresistance (TMR) is predicted which
can be controlled by an applied magnetic field. This phenomenon relates to the
quantum well states in the middle metallic layer. The corresponding resonances
in the current and the TMR are drastically phase shifted under positive and
negative voltage.Comment: 10 pages, 4 Postscript figures, submitted to Europhys. Let
Resonance magneto-resistance in double barrier structure with spin-valve
The conductance and tunnel magneto-resistance (TMR) of the double barrier
magnetic tunnel junction with spin-valve sandwich (F/P/F) inserted between two
insulating barrier, are theoretically investigated. It is shown, that resonant
tunnelling, due to the quantum well states of the electron confined between two
barriers, sharply depends on the mutual orientation of the magnetizations of
ferromagnetic layers F. The calculated optimistic value of TMR exceeds 2000% .Comment: 3 pages, 4 figure
Artificial ferroelectricity due to anomalous Hall effect in magnetic tunnel junctions
We theoretically investigated Anomalous Hall Effect (AHE) and Spin Hall
Effect (SHE) transversally to the insulating spacer O, in magnetic tunnel
junctions of the form F/O/F where F are ferromagnetic layers and O represents a
tunnel barrier. We considered the case of purely ballistic (quantum mechanical)
transport, taking into account the assymetric scattering due to spin-orbit
interaction in the tunnel barrier. AHE and SHE in the considered case have a
surface nature due to proximity effect. Their amplitude is in first order of
the scattering potential. This contrasts with ferromagnetic metals wherein
these effect are in second (side-jump scattering) and third (skew scattering)
order on these potentials. The value of AHE voltage in insulating spacer may be
much larger than in metallic ferromagnetic electrodes. For the antiparallel
orientation of the magnetizations in the two F-electrodes, a spontaneous Hall
voltage exists even at zero applied voltage. Therefore an insulating spacer
sandwiched between two ferromagnetic layers can be considered as exhibiting a
spontaneous ferroelectricity
Does Giant Magnetoresistance Survive in Presence of Superconducting Contact?
The giant magnetoresistance (GMR) of ferromagnetic bilayers with a
superconducting contact (F1/F2/S) is calculated in ballistic and diffusive
regimes. As in spin-valve, it is assumed that the magnetization in the two
ferromagnetic layers F1 and F2 can be changed from parallel to antiparallel. It
is shown that the GMR defined as the change of conductance between the two
magnetic configurations is an oscillatory function of the thickness of F2 layer
and tends to an asymptotic positive value at large thickness. This is due to
the formation of quantum well states in F2 induced by Andreev reflection at the
F2/S interface and reflection at F1/F2 interface in antiparallel configuration.
In the diffusive regime, if only spin-dependent scattering rates in the
magnetic layers are considered (no difference in Fermi wave-vectors between
spin up and down electrons) then the GMR is supressed due to the mixing of spin
up and down electron-hole channels by Andreev reflection.Comment: 7 pages, 4 figures, submitted to Phys.Rev.Let
Spin-dependent diffraction at ferromagnetic/spin spiral interface
Spin-dependent transport is investigated in ballistic regime through the
interface between a ferromagnet and a spin spiral. We show that spin-dependent
interferences lead to a new type of diffraction called "spin-diffraction". It
is shown that this spin-diffraction leads to local spin and electrical currents
along the interface. This study also shows that in highly non homogeneous
magnetic configuration (non adiabatic limit), the contribution of the
diffracted electrons is crucial to describe spin transport in such structures
- …