Quantification of propagating and standing surface acoustic waves by stroboscopic X-ray photoemission electron microscopy.
The quantification of surface acoustic waves (SAWs) in LiNbO3 piezoelectric crystals by stroboscopic X-ray photoemission electron microscopy (XPEEM), with a temporal smearing below 80 ps and a spatial resolution below 100 nm, is reported. The contrast mechanism is the varying piezoelectric surface potential associated with the SAW phase. Thus, kinetic energy spectra of photoemitted secondary electrons measure directly the SAW electrical amplitude and allow for the quantification of the associated strain. The stroboscopic imaging combined with a deliberate detuning allows resolving and quantifying the respective standing and propagating components of SAWs from a superposition of waves. Furth…
Piezo-electrical control of gyration dynamics of magnetic vortices
In this work, we first statically image the electrically controlled magnetostatic configuration of magnetic vortex states and then we dynamically image the time-resolved vortex core gyration tuned by electric fields. We demonstrate the manipulation of the vortex core gyration orbit by engineering the magnetic anisotropies. We achieve this by electric fields in a synthetic heterostructure consisting of a piezoelement coupled with magnetostrictive microstructures, where the magnetic anisotropy can be controlled by strain. We directly show the strong impact of the tailored anisotropy on the static shape of the vortex state and the dynamic vortex core orbit. The results demonstrate the possibil…
Simultaneous imaging of strain waves and induced magnetization dynamics at the nanometer scale
Changes in strain can be used to modify electronic and magnetic properties in crystal structures, to manipulate nanoparticles and cells, or to control chemical reactions. The magneto-elastic (ME) effect--the change of magnetic properties caused by the elastic deformation (strain) of a magnetic material--has been proposed as an alternative approach to magnetic fields for the low power control of magnetization states of nanoelements since it avoids charge currents, which entail ohmic losses. Multiferroic heterostructures \cite{Zheng2004} and nanocomposites have exploited this effect in search of electric control of magnetic states, mostly in the static regime. Quantitative studies combining s…
Magnetic configurations in nanostructured Co2MnGa thin film elements
The magnetic configuration of nanostructured elements fabricated from thin films of the Heusler compound Co2MnGa was determined by high-resolution x-ray magnetic microscopy, and the magnetic properties of continuous Co2MnGa thin films were determined by magnetometry measurements. A four-fold magnetic anisotropy with an anisotropy constant of kJ m−3 was deduced, and x-ray microscopy measurements have shown that the nanostructured Co2MnGa elements exhibit reproducible magnetic states dominated by shape anisotropy, with a minor contribution from the magneto-crystalline anisotropy, showing that the spin structure can be tailored by judiciously choosing the geometry.
Direct imaging of delayed magneto-dynamic modes induced by surface acoustic waves.
The magnetoelastic effect—the change of magnetic properties caused by the elastic deformation of a magnetic material—has been proposed as an alternative approach to magnetic fields for the low-power control of magnetization states of nanoelements since it avoids charge currents, which entail ohmic losses. Here, we have studied the effect of dynamic strain accompanying a surface acoustic wave on magnetic nanostructures in thermal equilibrium. We have developed an experimental technique based on stroboscopic X-ray microscopy that provides a pathway to the quantitative study of strain waves and magnetization at the nanoscale. We have simultaneously imaged the evolution of both strain and magne…