110 research outputs found
Giant spin-vorticity coupling excited by shear-horizontal surface acoustic waves
A non-magnetic layer can inject spin-polarized currents into an adjacent
ferromagnetic layer via spin vorticity coupling (SVC), inducing spin wave
resonance (SWR). In this work, we present the theoretical model of SWR
generated by shear-horizontal surface acoustic wave (SH-SAW) via SVC, which
contains distinct vorticities from well-studied Rayleigh SAW. Both Rayleigh-
and SH-SAW delay lines have been designed and fabricated with a Ni81Fe19/Cu
bilayer integrated on ST-cut quartz. Given the same wavelength, the measured
power absorption of SH-SAW is four orders of magnitudes higher than that of the
Rayleigh SAW. In addition, a high-order frequency dependence of the SWR is
observed in the SH-SAW, indicating SVC can be strong enough to compare with
magnetoelastic coupling
Observation of Enhanced Dynamic {\Delta}G effect near Ferromagnetic Resonance Frequency
The field-dependence elastic modulus of magnetostrictive films, also called
{\Delta}E or {\Delta}G effect, is crucial for ultrasensitive magnetic field
sensors based on surface acoustic waves (SAWs). In spite of a lot of successful
demonstrations, rare attention was paid to the frequency-dependence of
{\Delta}E or {\Delta}G effect. In current work, shear horizontal-type SAW delay
lines coated with a thin FeCoSiB layer have been studied at various frequencies
upon applying magnetic fields. The change of shear modulus of FeCoSiB has been
extracted by measuring the field-dependent phase shift of SAWs. It is found
that the {\Delta}G effect is significantly enhanced at high-order harmonic
frequencies close to the ferromagnetic resonance frequency, increasing by ~82%
compared to that at the first SAW mode (128 MHz). In addition, the smaller the
effective damping factor of magnetostrictive layer, the more pronounced
{\Delta}G effect can be obtained, which is explained by our proposed dynamic
magnetoelastic coupling model
Dynamic control of spin wave spectra using spin-polarized currents
We describe a method of controlling the spin wave spectra dynamically in a
uniform nanostripe waveguide through spin-polarized currents. A stable periodic
magnetization structure is observed when the current flows vertically through
the center of nanostripe waveguide. After being excited, the spin wave is
transmitted at the sides of the waveguide. Numerical simulations of spin-wave
transmission and dispersion curves reveal a single, pronounced band gap.
Moreover, the periodic magnetization structure can be turned on and off by the
spin-polarized current. The switching process from full rejection to full
transmission takes place within less than 3ns. Thus, this type magnonic
waveguide can be utilized for low-dissipation spin wave based filters.Comment: 10 pages, 5 figures, submitted to AP
Enhanced Terahertz Radiation Generation of Photoconductive Antennas Based on Manganese Ferrite Nanoparticles
This paper presents a significant effect of manganese ferrite nanoparticles (MnFe2O4 NPs) on the increase of the surface photoconductivity of semiconductors. Herein, the optical characterization of photo-excited carriers of silicon coated with MnFe2O4 NPs was studied by using THz time-domain spectroscopy (THz-TDs). We observed that silicon coated with MnFe2O4 NPs provided a significantly enhanced attenuation of THz radiation in comparison with bare silicon substrates under laser irradiation. The experimental results were assessed in the context of a surface band structure model of semiconductors. In addition, photoconductive antennas coated with MnFe2O4 NPs significantly improved the efficiency of THz radiation generation and signal to noise ratio of the THz signal. This work demonstrates that coating with MnFe2O4 NPs could improve the overall performance of THz systems, and MnFe2O4 NPs could be further used for the implementation of novel optical devicesQ.Z. acknowledges a fellowship from the Chinese Scholarship Council. Part of the project was funded by the European Commission (grant Future NanoNeeds to WJP). Financial support from MINECO (MAT2015–74381-JIN to B.P., RYC-2014–16962 to P.dP.), the ConsellerÃa de Cultura, Educación e Ordenación Universitaria (Centro singular de investigación de Galicia accreditation 2016–2019, ED431G/09), and the European Regional Development Fund (ERDF) is gratefully acknowledgedS
Self-Assembled BaTiO3-MnZnFe2O4 Nanocomposite Films
Self-assembled nanocomposite BaTiO3-Mn0.4Zn0.87Fe2O4 magnetodielectric films have been grown on (001)-oriented SrTiO3 substrates by a pulsed laser deposition method. High resolution X-ray diffraction shows that both BaTiO3 and MnZn-ferrite phases are epitaxial along the out-of-plane direction with a 0–3 composite structure in spite of very large lattice mismatch. The magnetic, ferroelectric, and dielectric properties of the nanocomposite films are reported. A saturated magnetization of 330 emu/cc and double remanent polarization of 40 μC/cm2 were obtained. Structural and compositional factors limiting the effective permeability and the dielectric constant will be discussed
The adjustable anisotropy field in FeCoTiO/SiO2/FeCoTiO trilayer films by oblique sputtering and stripe patterning
A series of FeCoTiO thin films were deposited on Si (100) substrates using oblique sputtering and stripe patterning at the same time and the static and high frequency magnetic properties were studied in details. For the single-layered films, if the anisotropy fields induced by the two methods are in the same direction, the effective anisotropy field will be greatly enhanced, closed to 300 Oe. But if the two anisotropy fields are perpendicular to each other, there will be an opposite result. In the FM/NM/FM sandwich structures, the influence of shape anisotropy will be suppressed by the exchange coupling effect between the two FM layers. The resonance frequency and permeability are still above 3.5 GHz and 75 even the width of stripes change from 40 µm to 10 µm
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