Magneto-elastic (or "straintronic") switching has emerged as an extremely energy-efficient mechanism for switching the magnetization of magnetostrictive nanomagnets in magnetic memory, logic and non-Boolean circuits. Here, we investigate the ultrafast magneto-dynamics associated with straintronic switching in a single quasi-elliptical magnetostrictive Co nanomagnet deposited on a piezoelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) substrate using time-resolved magneto-optical Kerr effect (TR-MOKE) measurements. The pulsed laser pump beam in the TR-MOKE plays a dual role: it causes precession of the nanomagnet's magnetization about an applied bias magnetic field and it also generates surface acoustic waves (SAWs) in the piezoelectric substrate that produce periodic strains in the magnetostrictive nanomagnet and modulate the precessional dynamics. This modulation gives rise to intriguing hybrid magneto-dynamical modes in the nanomagnet, with rich spin wave texture. The characteristic frequencies of these modes are 5-15 GHz, indicating that strain can affect magnetization in a magnetostrictive nanomagnet in time scales much smaller than 1 ns (~100 ps). This can enable ~10 GHz-range magneto-elastic nanooscillators that are actuated by strain instead of a spin-polarized current, as well as ultrafast magneto-electric generation of spin waves for magnonic logic circuits, holograms, etc.

Antennas typically have emission/radiation efficiencies bounded by A/λ2(A < λ2) where A is the emitting area and λ is the emitted wavelength. That makes it challenging to miniaturize antennas to extreme subwavelength dimensions without severely compromising their efficiencies. To overcome this challenge, an electromagnetic (EM) antenna is actuated with a surface acoustic wave (SAW) whose wavelength is about five orders of magnitude smaller than the EM wavelength at the same frequency. This allows to implement an extreme subwavelength EM antenna, radiating an EM wave of wavelength λ = 2 m, whose emitting area is ≈10−8 m2 (A/λ2 = 2.5 × 10−9), and whose measured radiation efficiency exceeds the A/λ2 limit by over 105. The antenna consists of magnetostrictive nanomagnets deposited on a piezoelectric substrate. A SAW launched in the substrate with an alternating electrical voltage periodically strains the nanomagnets and rotates their magnetizations owing to the Villari effect. The oscillating magnetizations emit EM waves at the frequency of the SAW. These extreme subwavelength antennas that radiate with efficiencies a few orders of magnitude larger than the A/λ2 limit allow drastic miniaturization of communication systems.

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Ferromagnetic nanostripes have gained massive attention due to their intriguing magnetic properties associated with dimensional confinements and shape anisotropy leading toward potential applications in magnetic storage, memory, and spin‐wave‐based devices. Consequently, reconfiguration of their static and dynamic magnetic properties by the geometric parameters and external field is imperative. Here, a combined experimental and numerical study of the reconfigurable spin‐wave dynamics in arrays of ferromagnetic nanostripes by the stripe thickness and external magnetic field strength and orientation is presented. Different uniform, localized, and standing spin waves in the nanostripes and their monotonic and nonmonotonic variation, including mode merging with these parameters, are observed. The observed variations are interpreted with the aid of simulated spin configurations, magnetostatic field maps, and spin‐wave mode profiles. Further numerical study reveals anisotropic spin‐wave propagation in nanostripes for different thicknesses and in different bias‐field geometry opening potential applications in magnonic circuit components such as reconfigurable magnonic waveguides and omnidirectional spin‐wave emitters.

We introduce a new type of binary magnonic crystal, where Ni80Fe20 nanodots of two different sizes are diagonally connected forming a unit and those units are arranged in a square lattice. The magnetization dynamics of the sample is measured by using time-resolved magneto-optical Kerr effect microscope with varying magnitude and in-plane orientation (ϕ) of the bias magnetic field. Interestingly, at ϕ = 0°, the spin-wave mode profiles show frequency selective spatial localization of spin-wave power within the array. With the variation of ϕ in the range 0°<ϕ≤45°, we observe band narrowing due to localized to extended spin-wave mode conversion. Upon further increase of ϕ, the spin-wave modes slowly lose the extended nature and become fully localized again at 90°. We have extensively demonstrated the role of magnetostatic stray field distribution on the rotational symmetries obtained for the spin-wave modes. From micromagnetic simulations, we find that the dipoleexchange coupling between the nano-dots leads to remarkable modifications of the spin-wave mode profiles when compared with arrays of individual small and large dots. Numerically, we also show that the physical connection between the nano-dots provides more control points over the spin-wave propagation in the lattice at different orientations of bias magnetic field. This new type of binary magnonic crystal may find potential applications in magnonic devices such as spin-wave waveguide, filter, coupler, and other on-chip microwave communication devices. I. Introduction:Nanomagnets have huge applications in magnetic storage [1], memory [2], logic [3], sensors [4], other spintronics and biomedical devices [5,6]. One of the more recent and emerging fields based on nanomagnetism is magnonic crystals (MCs) [7], which are periodically modulated ferromagnetic materials, such as ferromagnetic nanodots [8], nanowire [9], nanoscale antidot arrays [10], where spin waves (SWs) are carrier waves. Due to their wavelength falling in the nanoscale regime for GHz to sub-THz frequency range spin-waves, MCs are ideally suited for nanoscale on-chip microwave communication devices. Those are also capable of forming magnonic minibands with allowed and forbidden frequencies [11][12][13]. By varying the physical and geometrical parameters of the artificial crystal, the nature of intra-element and inter-element magnetic field distributions within the array can be tuned, which in turn, modify its SW dynamics. A plethora of studies on the quasi-static and dynamic properties of 1-D, 2-D and 3-D MCs have been carried out due to their fundamental physical properties and their promising applications, such as spin-wave filter, coupler, phase shifter, splitter and other magnonic devices [14][15][16][17][18][19][20][21][22][23]. Recently, the entanglement between various spin-based phenomena has emerged as a new field, coined as magnon-spintronics [24]. Analogous to various natural or artificial crystals, introduction of bi-or multi-components can lead to a variation in the periodic potential ...