30 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
Magnetostrictive and magnetoelectric behavior of Fe–20 at. % Ga/Pb(Zr,Ti)O3 laminates
The magnetostrictive and magnetoelectric (ME) properties of laminate composites of Fe–20 at. % Ga and Pb(Zr,Ti)O3 (PZT) have been studied for laminates of different geometries. The results show that (i) a long-type magnetostrictive Fe–20 at. % Ga crystal plate oriented along 〈001〉c and magnetized in its longitudinal (or length) direction has higher magnetostriction than a disk-type one; and consequently (ii) a long-type Fe–20 at. % Ga/PZT laminate has a giant ME effect, and is sensitive to low-level magnetic fields
Intermediate ferroelectric orthorhombic and monoclinic MB phases in [110]- electric field cooled Pb(Mg1/3Nb2/3)O3-30%PbTiO3 crystals
Structural phase transformations of [110] electric field cooled
Pb(Mg1/3Nb2/3)O3-30%PbTiO3 (PMN-30%PT) crystals have been performed by x-ray
diffraction in a field-cooled (FC) condition. A phase sequence of
cubic(C)-tetragonal(T)-orthorhombic (O)-monoclinic (MB) was found on
field-cooling (FC); and a R-MB-O one was observed with increasing field
beginning from the zero field-cooled (ZFC) condition at room temperature. The
application of the [110] electric field induced a dramatic change in the phase
sequence in the FC condition, compared to the corresponding data for PMN-30%PT
crystals in a [001] field, which shows that the phase sequence in the FC
condition is altered by the crystallographic direction along which a modest
electric field (E) is applied. Only when E is applied along [110] are
intermediate O and MB phases observed.Comment: 10 pages, 8 figure
Fe–Ga/Pb(Mg1/3Nb2/3)O3–PbTiO3 magnetoelectric laminate composites
We have found large magnetoelectric (ME) effects in long-type laminate composites of Fe–20%Ga magnetostrictive alloys and piezoelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals. At lower frequencies, the ME voltage coefficient of a laminate with longitudinally magnetized and longitudinally polarized (i.e., L-L mode) layers was 1.41 V/Oe (or1.01 V/cm Oe). Near the natural resonant frequency ( ∼ 91 kHz) of the laminate, the ME voltage coefficients were found to be dramatically increased to 50.7 V/Oe (36.2 V/cm Oe)for the L-L mode. In addition, the laminate can detect a minute magnetic field as low as ∼ 2×10−12 T at resonance frequency, and ∼ 1×10−10 T at lower frequencies
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
Residual Stress Analysis of Stacked SnTe/Ge2Se3 Phase Change Memory Films using Vantec 2000 Area Detector
Residual stress in novel chalcogenide thin film stacks of polycrystalline SnTe and amorphous Ge2Se3 is measured using X-ray Diffraction (XRD). The as-deposited film stacks are annealed at different temperatures and the thermal dependence of stress is investigated. Stress evaluations are performed by 2 employing the sin ψ technique using a 2D area detector system. As-deposited samples are found to be compressively stressed and exhibit increasingly tensile thermal stress with increasing annealing temperature. Onset of crystallization of the bottom Ge2Se3 layer is indicated by a dip in the stress level in the 270 o C – 360 o C temperature range, due to volume shrinkage associated with the crystallization. Diffraction patterns of samples annealed at different temperatures indicate compositional changes that are attributed to inter-diffusion of ions between the two layers. The XRD profiles of samples annealed at 360 o C and 450 o C indicate the formation of a SnTe-GeSe solid solution. It is suggested that both, residual stress and temperature dependent compositional changes affect the measured d spacings. 1
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