379 research outputs found
Magnetic Domain Structure of La0.7Sr0.3MnO3 thin-films probed at variable temperature with Scanning Electron Microscopy with Polarization Analysis
The domain configuration of 50 nm thick La0.7SrMnO3 films has been directly
investigated using scanning electron microscopy with polarization analysis
(SEMPA), with magnetic contrast obtained without the requirement for prior
surface preparation. The large scale domain structure reflects a primarily
four-fold anisotropy, with a small uniaxial component, consistent with
magneto-optic Kerr effect measurements. We also determine the domain transition
profile and find it to be in agreement with previous estimates of the domain
wall width in this material. The temperature dependence of the image contrast
is investigated and compared to superconducting-quantum interference device
magnetometry data. A faster decrease in the SEMPA contrast is revealed, which
can be explained by the technique's extreme surface sensitivity, allowing us to
selectively probe the surface spin polarization which due to the double
exchange mechanism exhibits a distinctly different temperature dependence than
the bulk magnetization
Ultrabroadband single-cycle terahertz pulses with peak fields of 300 kV cm from a metallic spintronic emitter
To explore the capabilities of metallic spintronic thin-film stacks as a
source of intense and broadband terahertz electromagnetic fields, we excite a
W/CoFeB/Pt trilayer on a large-area glass substrate (diameter of 7.5 cm) by a
femtosecond laser pulse (energy 5.5 mJ, duration 40 fs, wavelength 800 nm).
After focusing, the emitted terahertz pulse is measured to have a duration of
230 fs, a peak field of 300 kV cm and an energy of 5 nJ. In particular,
the waveform exhibits a gapless spectrum extending from 1 to 10 THz at 10% of
amplitude maximum, thereby facilitating nonlinear control over matter in this
difficult-to-reach frequency range and on the sub-picosecond time scale.Comment: 7 pages, 4 figure
Thermal conductance of thin film YIG determined using Bayesian statistics
Thin film YIG (YFeO) is a prototypical material for
experiments on thermally generated pure spin currents and the spin Seebeck
effect. The 3-omega method is an established technique to measure the
cross-plane thermal conductance of thin films, but can not be used in YIG/GGG
(GaGdO) systems in its standard form. We use two-dimensional
modeling of heat transport and introduce a technique based on Bayesian
statistics to evaluate measurement data taken from the 3-omega method. Our
analysis method allows us to study materials systems that have not been
accessible with the conventionally used 3-omega analysis. Temperature dependent
thermal conductance data of thin film YIG are of major importance for
experiments in the field of spin-caloritronics. Here we show data between room
temperature and 10 K for films covering a wide thickness range as well as the
magnetic field effect on the thermal conductance between 10 K and 50 K
Tunable steady-state domain wall oscillator with perpendicular magnetic anisotropy
We theoretically study domain wall oscillations upon the injection of a dc
current through a geometrically constrained wire with perpendicular magnetic
anisotropy. The oscillation frequency spectrum can be tuned by the injected
current density, but additionally by the application of an external magnetic
field independent of the power. The results of analytical calculations are
supported by micromagnetic simulations based on the Landau-Lifshitz-Gilbert
equation. The simple concept of our localized steady-state oscillator might
prove useful as a nanoscale microwave generator with possible applications in
telecommunication or for rf-assisted writing in magnetic hard drives.Comment: 10 pages, 3 figure
Giant Spin Seebeck Effect through an Interface Organic Semiconductor
Interfacing an organic semiconductor C60 with a non-magnetic metallic thin
film (Cu or Pt) has created a novel heterostructure that is ferromagnetic at
ambient temperature, while its interface with a magnetic metal (Fe or Co) can
tune the anisotropic magnetic surface property of the material. Here, we
demonstrate that sandwiching C60 in between a magnetic insulator (Y3Fe5O12:
YIG) and a non-magnetic, strong spin-orbit metal (Pt) promotes highly efficient
spin current transport via the thermally driven spin Seebeck effect (SSE).
Experiments and first principles calculations consistently show that the
presence of C60 reduces significantly the conductivity mismatch between YIG and
Pt and the surface perpendicular magnetic anisotropy of YIG, giving rise to
enhanced spin mixing conductance across YIG/C60/Pt interfaces. As a result, a
600% increase in the SSE voltage (VLSSE) has been realized in YIG/C60/Pt
relative to YIG/Pt. Temperature-dependent SSE voltage measurements on
YIG/C60/Pt with varying C60 layer thicknesses also show an exponential increase
in VLSSE at low temperatures below 200 K, resembling the temperature evolution
of spin diffusion length of C60. Our study emphasizes the important roles of
the magnetic anisotropy and the spin diffusion length of the intermediate layer
in the SSE in YIG/C60/Pt structures, providing a new pathway for developing
novel spin-caloric materials
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