908 research outputs found
Magnetic critical properties and basal-plane anisotropy of SrIrO
The anisotropic magnetic properties of SrIrO are investigated, using
longitudinal and torque magnetometry. The critical scaling across of the
longitudinal magnetization is the one expected for the 2D XY universality
class. Modeling the torque for a magnetic field in the basal-plane, and taking
into account all in-plane and out-of-plane magnetic couplings, we derive the
effective 4-fold anisotropy 1 10 erg mole. Although
larger than for the cuprates, it is found too small to account for a
significant departure from the isotropic 2D XY model. The in-plane torque also
allows us to put an upper bound for the anisotropy of a field-induced shift of
the antiferromagnetic ordering temperature
Fel Oscillators with Tapered Undulators: Inclusion of Harmonic Generation and Pulse Propagation
We review the theory of FEL oscillators operating with tapered undulators. We
consider the case of a uniform tapering and introduce a parameter which
characterizes the effect of the tapering on the gain and on the saturation
intensity. We analyze the effect of the tapering on the FEL dynamics by
including the pulse propagation effects too. We analyze the importance of
tapering as a tool to model the optical pulse shapes and to control the higher
harmonic intensities
Sr 2 IrO 4 magnetic phase diagram, from resistivity
International audienceWe show that the transition to the antiferromagnetic state in zero magnetic field does show up in the transverse resistivity, for which we point out the possibility for a direct spin orientation effect. In an applied field, we propose that the transition is split into two lines, corresponding to in-plane and out-of-plane magnetic ordering. This picture is corroborated by transverse magnetization measurements. The magnetic phase diagram for Sr2IrO4 was investigated, using the angular dependence of the resistivity transverse to the IrO2 planes
Photon emission by an ultra-relativistic particle channeling in a periodically bent crystal
This paper is devoted to a detailed analysis of the new type of the undulator
radiation generated by an ultra-relativistic charged particle channeling along
a crystal plane, which is periodically bent by a transverse acoustic wave, as
well as to the conditions limiting the observation of this phenomenon. This
mechanism makes feasible the generation of electromagnetic radiation, both
spontaneous and stimulated, emitted in a wide range of the photon energies,
from X- up to gamma-rays
Light controlled magnetoresistance and magnetic field controlled photoresistance in CoFe film deposited on BiFeO3
We present a magnetoresistive-photoresistive device based on the interaction
of a piezomagnetic CoFe thin film with a photostrictive BiFeO3 substrate that
undergoes light-induced strain. The magnitude of the resistance and
magnetoresistance in the CoFe film can be controlled by the wavelength of the
incident light on the BiFeO3. Moreover, a light-induced decrease in anisotropic
magnetoresistance is detected due to an additional magnetoelastic contribution
to magnetic anisotropy of the CoFe film. This effect may find applications in
photo-sensing systems, wavelength detectors and can possibly open a research
development in light-controlled magnetic switching properties for next
generation magnetoresistive memory devices.Comment: 5 pages, 4 figures, journal pape
Coherent and incoherent bands in La and Rh doped Sr3Ir2O7
In Sr2IrO4 and Sr3Ir2O7, correlations, magnetism and spin-orbit coupling
compete on similar energy scales, creating a new context to study
metal-insulator transitions (MIT). We use here Angle-Resolved photoemission to
investigate the MIT as a function of hole and electron doping in Sr3Ir2O7,
obtained respectively by Ir/Rh and Sr/La substitutions. We show that there is a
clear reduction as a function of doping of the gap between a lower and upper
band on both sides of the Fermi level, from 0.2eV to 0.05eV. Although these two
bands have a counterpart in band structure calculations, they are characterized
by a very different degree of coherence. The upper band exhibits clear
quasiparticle peaks, while the lower band is very broad and loses weight as a
function of doping. Moreover, their ARPES spectral weights obey different
periodicities, reinforcing the idea of their different nature. We argue that a
very similar situation occurs in Sr2IrO4 and conclude that the physics of the
two families is essentially the same
Angle-resolved photoemission study of the role of nesting and orbital orderings in the antiferromagnetic phase of BaFe2As2
We present a detailed comparison of the electronic structure of BaFe2As2 in
its paramagnetic and antiferromagnetic (AFM) phases, through angle-resolved
photoemission studies. Using different experimental geometries, we resolve the
full elliptic shape of the electron pockets, including parts of dxy symmetry
along its major axis that are usually missing. This allows us to define
precisely how the hole and electron pockets are nested and how the different
orbitals evolve at the transition. We conclude that the imperfect nesting
between hole and electron pockets explains rather well the formation of gaps
and residual metallic droplets in the AFM phase, provided the relative parity
of the different bands is taken into account. Beyond this nesting picture, we
observe shifts and splittings of numerous bands at the transition. We show that
the splittings are surface sensitive and probably not a reliable signature of
the magnetic order. On the other hand, the shifts indicate a significant
redistribution of the orbital occupations at the transition, especially within
the dxz/dyz system, which we discuss
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