Symmetry of the Magnetoelastic Interaction of Rayleigh and Shear Horizontal Magnetoacoustic Waves in Nickel Thin Films on LiTaO3

Abstract

We study the interaction of Rayleigh and shear horizontal surface acoustic waves (SAWs) with spin waves in thin Ni films on a piezoelectric LiTaO 3 substrate, which supports both SAW modes simultaneously. Because Rayleigh and shear horizontal modes induce different strain components in the Ni thin films, the symmetries of the magnetoelastic driving fields, of the magnetoelastic response, and of the transmission nonreciprocity differ for both SAW modes. Our experimental findings are well explained by a theoretical model based on a modified Landau-Lifshitz-Gilbert approach. We show that the symmetries of the magnetoelastic response driven by Rayleigh and shear horizontal SAWs complement each other, which makes it possible to excite spin waves for any relative orientation of magnetization and SAW propagation direction and, moreover, can be utilized to characterize surface strain components of unknown acoustic wave modes.

Nonreciprocal Magnetoacoustic Waves in Dipolar-Coupled Ferromagnetic Bilayers

“…If the propagation direction of the SAW is inverted, the strain xz,0 changes sign (with respect to xx,0 ) and the helicities of the driving fields h l are inverted. This results, together with the favored, righthanded rotational sense of the magnetization precession, in a nonreciprocal excitation efficiency that has so far only been studied in magnetic single layers [8][9][10][11][12][13][14].…”

“…Moreover, coupling SAWs with spin waves (SWs) in magnetic media is a straightforward approach to obtain nonreciprocity. In this case the SAW-SW coupling mechanism itself is already nonreciprocal, because of a helicity mismatch between the SAW-induced magnetoacoustic driving fields and the fixed chirality of the magnetization precession [8][9][10][11][12][13][14]. Furthermore, the SW dispersion relation can be nonreciprocal.…”

Preface: Celebrating the 70th Anniversary of School of Mechanical Science and Engineering, Huazhong University of Science and Technology

“…Next, we will discuss the dispersion relations of interacting nonreciprocal SWs and SH-SAWs. It is recently reported that SH-SAWs are more efficient to excite SWs than well-studied Rayleigh-type SAWs [39]. We will limit our discussion within MEC since it is much stronger for magnetostrictive materials than other effects, such as spinvorticity coupling [40] and magneto-rotation coupling [41].…”

“…For the SH-SAWs,  can be expressed as [11,39]: SAWs, both k and fSW increases rapidly with increasing  due to the increasing intralayer dipolar field [44]. Clearly, a relatively low  angle facilitates the coupling between SAWs and SWs at low k .…”

Parametric Excitation and Instabilities of Spin Waves driven by Surface Acoustic Waves

“…In recent years, the focus in the field of dynamic magnetoelasticity has shifted towards coupling with surface acoustic waves (SAW) in hybrid magneto-elastic structures [13][14][15], since they offer a large variety of different modes leading to interesting coupling phenomena [16,17]. In addition, their spatial localization to the surface makes their interaction with thin (magnetic) films placed on top of the wave-carrying sub-strate much more efficient which opens various new opportunities for hybrid systems and devices [18,19].…”