Irreversible magnetization switching using surface acoustic waves

Abstract

An analytical and numerical approach is developped to pinpoint the optimal experimental conditions to irreversibly switch magnetization using surface acoustic waves (SAWs). The layers are magnetized perpendicular to the plane and two switching mechanisms are considered. In precessional switching, a small in-plane field initially tilts the magnetization and the passage of the SAW modifies the magnetic anisotropy parameters through inverse magneto-striction, which triggers precession, and eventually reversal. Using the micromagnetic parameters of a fully characterized layer of the magnetic semiconductor (Ga,Mn)(As,P), we then show that there is a large window of accessible experimental conditions (SAW amplitude/wave-vector, field amplitude/orientation) allowing irreversible switching. As this is a resonant process, the influence of the detuning of the SAW frequency to the magnetic system's eigenfrequency is also explored. Finally, another -non-resonantswitching mechanism is briefly contemplated, and found to be applicable to (Ga,Mn)(As,P): SAWassisted domain nucleation. In this case, a small perpendicular field is applied opposite the initial magnetization and the passage of the SAW lowers the domain nucleation barrier.

Surface-acoustic-wave-driven ferromagnetic resonance in (Ga,Mn)(As,P) epilayers

“…The generated strain (ε max ≈ 10 −5 ) is for now about five times too small to obtain magnetization reversal, as sketched in the predictive diagram of Ref. [2]. This has been confirmed by the robust linearity of the observed effect versus acoustic power.…”

“…The opposite effect, inverse magnetostriction, whereby magnetization can be changed upon application of a strain, is particularly relevant to magnetic data storage technologies as a possible route towards induction-free data manipulation when used dynamically. It has been proposed for magnetization switching through resonant [2,3] or nonresonant processes [4,5], the latter possibly at play in early results of surface acoustic wave (SAW)-induced lowering of coercivity in Galfenol films [6]. In the case of precessional (resonant) switching, two features are necessary: sizable magnetoacoustic coupling (to trigger precession), and a highly nonlinear system (to force wide, noncircular precession needed for magnetization reversal).…”

“…The low Curie temperature (100-180 K) of these compounds makes applications somewhat remote for now, but their magnetization precession frequencies are close to accessible SAW frequencies (GHz) and their small and * thevenard@insp.jussieu.fr tunable magnetic anisotropy make them good candidates to test SAW-assisted magnetization switching [2]. Moreover thanks to the semiconducting nature of host lattice [15,16], their magnetic properties can easily be band engineered and their magnetostrictive coefficients vary strongly with temperature, making them a good test-bench material to develop and validate theoretical models.…”

Determination of magnetoelastic oscillations in ferrite plate with different values of anisotropy constant

“…The nonlinear magnetoelastic dynamics of films and plates is a rapidly developing region [2][3][4][5][6]. Thus, the use of optimization methods in the study of magnetoacoustic interactions is also an urgent task.…”

Vector network analyzer measurement of the amplitude of an electrically excited surface acoustic wave and validation by X-ray diffraction

“…[2][3][4][5] In more academic environments, they are used in magnetism, in microfluidics and in quantum systems. In magnetism, SAWs can assist magnetization switching in ferromagnetic magnetostrictive thin films and nanostructures [6][7][8][9][10] for magnetic data storage application. The efficiency of that switching is related to the amplitude of the SAW.…”