669 research outputs found
Antiferromagnetic resonances in superconductor-ferromagnet multilayers
In this work, we study magnetization dynamics in superconductor-ferromagnet
(S-F) thin-film multilayer. Theoretical considerations supported by the
broad-band ferromagnetic resonance spectroscopy reveal development of acoustic
and optic resonance modes in S-F multilayers at significantly higher
frequencies in comparison to the Kittel mode of individual F-layers. These
modes are formed due to antiferromagnetic-like interaction between F-layers via
shared circulating superconducting currents in S-layers. The gap between
resonance modes is determined by the thickness and superconducting penetration
depth in S-layers. Overall, rich spectrum of S-F multilayers and its tunability
opens wide prospects for application of these multialyers in magnonics as well
as in various superconducting hybrid systems.Comment: 5 pages, 4 figures, 34 reference
Sharp estimates of integral functionals on classes of functions with small mean oscillation
We unify several Bellman function problems into one setting. For that purpose
we define a class of functions that have, in a sense, small mean oscillation
(this class depends on two convex sets in ). We show how the unit
ball in the space, or a Muckenhoupt class, or a Gehring class
can be described in such a fashion. Finally, we consider a Bellman function
problem on these classes, discuss its solution and related questions.Comment: 7 page
Magnetization Dynamics in Proximity-Coupled Superconductor-Ferromagnet-Superconductor Multilayers:II. Thickness Dependence of the Superconducting Torque
In this work, we study magnetization dynamics in superconductor-ferromagnet-superconductor thin-film structures. Results of the broad-band ferromagnetic resonance spectroscopy are reported for a large set of samples with varied thickness of both superconducting and ferromagnetic layers in a wide frequency, field, and temperature ranges. Experimentally the one-dimensional anisotropic action of superconducting torque on magnetization dynamics is established; its dependence on thickness of layers is revealed. It is demonstrated that experimental findings support the recently proposed mechanism of the superconducting torque formation via the interplay between the superconducting imaginary conductance and magnetization precession at superconductor-ferromagnet interfaces. Microwave spectroscopy studies in this work are supplemented by investigations of the crystal structure and the microstructure of studied multilayers.</p
Fourier transform spectroscopy and coupled-channel deperturbation treatment of the A1Sigma+ ~ b3Pi complex of KCs molecule
The laser induced fluorescence (LIF) spectra A1Sigma ~ b3Pi --> X1Sigma+ of
KCs dimer were recorded in near infrared region by Fourier Transform
Spectrometer with a resolution of 0.03 cm-1. Overall more than 200 LIF spectra
were rotationally assigned to 39K133Cs and 41K133Cs isotopomers yielding with
the uncertainty of 0.003-0.01 cm-1 more than 3400 rovibronic term values of the
strongly mixed singlet A1Sigma+ and triplet b3Pi states. Experimental data
massive starts from the lowest vibrational level v_A=0 of the singlet and
nonuniformly cover the energy range from 10040 to 13250 cm-1 with rotational
quantum numbers J from 7 to 225. Besides of the dominating regular A1Sigma+ ~
b3P Omega=0 interactions the weak and local heterogenous A1S+ ~ b3P Omega=1
perturbations have been discovered and analyzed. Coupled-channel deperturbation
analysis of the experimental 39K133Cs e-parity termvalues of the A1S+ ~ b3P
complex was accomplished in the framework of the phenomenological 4 x 4
Hamiltonian accounting implicitly for regular interactions with the remote
states manifold. The resulting diabatic potential energy curves of the
interacting states and relevant spin-orbit coupling matrix elements defined
analytically by Expanded Morse Oscillators model reproduce 95% of experimental
data field of the 39K133Cs isotopomer with a standard deviation of 0.004 cm-1
which is consistent with the uncertainty of the experiment. Reliability of the
derived parameters was additionally confirmed by a good agreement between the
predicted and experimental termvalues of 41K133Cs isotopomer. Calculated
intensity distributions in the A ~ b --> X LIF progressions are also consistent
with their experimental counterparts.Comment: 17 pages, 14 figure
Double Fe-impurity charge state in the topological insulator BiSe
The influence of individual impurities of Fe on the electronic properties of
topological insulator BiSe is studied by Scanning Tunneling Microscopy.
The microscope tip is used in order to remotely charge/discharge Fe impurities.
The charging process is shown to depend on the impurity location in the
crystallographic unit cell, on the presence of other Fe impurities in the close
vicinity, as well as on the overall doping level of the crystal. We present a
qualitative explanation of the observed phenomena in terms of tip-induced local
band bending. Our observations evidence that the specific impurity neighborhood
and the position of the Fermi energy with respect to the Dirac point and bulk
bands have both to be taken into account when considering the electron
scattering on the disorder in topological insulators.Comment: 10 pages, accepted for publication in Applied Physics Letters, minor
bugs were correcte
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