299 research outputs found
Dephasing Effects by Ferromagnetic Boundary on Resistivity in Disordered Metallic Layer
The resistivity of disordered metallic layer sandwiched by two ferromagnetic
layers at low-temperature is investigated theoretically. It is shown that the
magnetic field acting at the interface does not affect the classical Boltzmann
resistivity but causes a dephasing among electrons in the presence of the
spin-orbit interaction, suppressing the anti-localization due to the spin-orbit
interaction. The dephasing turns out to be stronger in the case where the
magnetization of the two layers is parallel, contributing to a positive
magnetoresistance close to a switching field at low temperature.Comment: 11 pages, 3 figures. Title modified in journal versio
Phase Diagram of Multilayer Magnetic Structures
Multilayer "ferromagnet-layered antiferromagnet" (Fe/Cr) structures
frustrated due to the roughness of layer interfaces are studied by numerical
modeling methods. The "thickness-roughness" phase diagrams for the case of thin
ferromagnetic film on the surface of bulk antiferromagnet and for two
ferromagnetic layers separated by an antiferromagnetic interlayer are obtained
and the order parameter distributions for all phases are found. The phase
transitions nature in such systems is considered. The range of applicability
for the "magnetic proximity model" proposed by Slonczewski is evaluated.Comment: 8 pages, 8 figure
Influence of uncorrelated overlayers on the magnetism in thin itinerant-electron films
The influence of uncorrelated (nonmagnetic) overlayers on the magnetic
properties of thin itinerant-electron films is investigated within the
single-band Hubbard model. The Coulomb correlation between the electrons in the
ferromagnetic layers is treated by using the spectral density approach (SDA).
It is found that the presence of nonmagnetic layers has a strong effect on the
magnetic properties of thin films. The Curie temperatures of very thin films
are modified by the uncorrelated overlayers. The quasiparticle density of
states is used to analyze the results. In addition, the coupling between the
ferromagnetic layers and the nonmagnetic layers is discussed in detail. The
coupling depends on the band occupation of the nonmagnetic layers, while it is
almost independent of the number of the nonmagnetic layers. The induced
polarization in the nonmagnetic layers shows a long-range decreasing
oscillatory behavior and it depends on the coupling between ferromagnetic and
nonmagnetic layers.Comment: 9 pages, RevTex, 6 figures, for related work see:
http://orion.physik.hu-berlin.d
Exchange Field Induced Magnetoresistance in Colossal Magnetoresistance Manganites
The effect of an exchange field on electrical transport in thin films of
metallic ferromagnetic manganites has been investigated. The exchange field was
induced both by direct exchange coupling in a ferromagnet/antiferromagnet
multilayer and by indirect exchange interaction in a ferromagnet/paramagnet
superlattice. The electrical resistance of the manganite layers was found to be
determined by the absolute value of the vector sum of the effective exchange
field and the external magnetic field.Comment: 5 pages, 4 figure
Spin-Polarized Transprot through Double Quantum Dots
We investigate spin-polarized transport phenomena through double quantum dots
coupled to ferromagnetic leads in series. By means of the slave-boson
mean-field approximation, we calculate the conductance in the Kondo regime for
two different configurations of the leads: spin-polarization of two
ferromagnetic leads is parallel or anti-parallel. It is found that transport
shows some remarkable properties depending on the tunneling strength between
two dots. These properties are explained in terms of the Kondo resonances in
the local density of states.Comment: 8 pages, 11 figure
Angular dependence of domain wall resistivity in SrRuO films
is a 4d itinerant ferromagnet (T 150 K) with
stripe domain structure. Using high-quality thin films of SrRuO we study
the resistivity induced by its very narrow ( nm) Bloch domain walls,
(DWR), at temperatures between 2 K and T as a function of the
angle, , between the electric current and the ferromagnetic domains
walls. We find that which provides the first experimental
indication that the angular dependence of spin accumulation contribution to DWR
is . We expect magnetic multilayers to exhibit a similar
behavior.Comment: 5 pages, 5 figure
Self-similar magnetoresistance of Fibonacci ultrathin magnetic films
We study numerically the magnetic properties (magnetization and
magnetoresistance) of ultra-thin magnetic films (Fe/Cr) grown following the
Fibonacci sequence. We use a phenomenological model which includes Zeeman,
cubic anisotropy, bilinear and biquadratic exchange energies. Our physical
parameters are based on experimental data recently reported, which contain
biquadratic exchange coupling with magnitude comparable to the bilinear
exchange coupling. When biquadratic exchange coupling is sufficiently large a
striking self-similar pattern emerges.Comment: 5 pages, 5 EPS figures, REVTeX, accepted for publication in Phys.
Rev.
Field-driven femtosecond magnetization dynamics induced by ultrastrong coupling to THz transients
Controlling ultrafast magnetization dynamics by a femtosecond laser is
attracting interest both in fundamental science and industry because of the
potential to achieve magnetic domain switching at ever advanced speed. Here we
report experiments illustrating the ultrastrong and fully coherent light-matter
coupling of a high-field single-cycle THz transient to the magnetization vector
in a ferromagnetic thin film. We could visualize magnetization dynamics which
occur on a timescale of the THz laser cycle and two orders of magnitude faster
than the natural precession response of electrons to an external magnetic
field, given by the Larmor frequency. We show that for one particular
scattering geometry the strong coherent optical coupling can be described
within the framework of a renormalized Landau Lifshitz equation. In addition to
fundamentally new insights to ultrafast magnetization dynamics the coherent
interaction allows for retrieving the complex time-frequency magnetic
properties and points out new opportunities in data storage technology towards
significantly higher storage speed.Comment: 25 page
Giant magnetic enhancement in Fe/Pd films and its influence on the magnetic interlayer coupling
The magnetic properties of thin Pd fcc(001) films with embedded monolayers of
Fe are investigated by means of first principles density functional theory. The
induced spin polarization in Pd is calculated and analyzed in terms of quantum
interference within the Fe/Pd/Fe bilayer system. An investigation of the
magnetic enhancement effects on the spin polarization is carried out and its
consequences for the magnetic interlayer coupling are discussed. In contrast to
{\it e.g.} the Co/Cu fcc(001) system we find a large effect on the magnetic
interlayer coupling due to magnetic enhancement in the spacer material. In the
case of a single embedded Fe monolayer we find aninduced Pd magnetization
decaying with distance from the magnetic layer as ~ with
. For the bilayer system we find a giant magnetic
enhancement (GME) that oscillates strongly due to interference effects. This
results in a strongly modified magnetic interlayer coupling, both in phase and
magnitude, which may not be described in the pure
Ruderman-Kittel-Kasuya-Yoshida (RKKY) picture. No anti-ferromagnetic coupling
was found and by comparison with magnetically constrained calculations we show
that the overall ferromagnetic coupling can be understood from the strong
polarization of the Pd spacer
1/f noise in magnetic Ni80Fe20 single layers and Ni80Fe20/Cu multilayers
We have investigated the room temperature 1/f noise of microstructured soft magnetic Ni80Fe20 films, showing the anisotropic magnetoresistance effect, and of Ni80Fe20/Cu magnetic multilayers, showing the giant magnetoresistance effect. We find that the 1/f noise in magnetic multilayers is considerably enhanced with respect to the noise of the single domain layer, which sets a limit on the usability of giant magnetoresistance materials for low-frequency applications
- …