Dramatic Influence of the Magnetoelectric Effect on the Existence of the New SH-SAWs Propagating in Magnetoelectroelastic Composites

Abstract

This comparative study acquaints the reader with some properties of the eighth and tenth new shear-horizontal surface acoustic waves (SH-SAWs) propagating along the free surface of the magnetoelectroelastic (6 mm) medium. These new nondispersive SH-SAWs cannot exist when the electromagnetic constant α is equal to zero. The piezoelectromagnetic SH bulk acoustic wave and the surface Bleustein-Gulyaev-Melkumyan (BGM) wave are also chosen for comparison. The main problem of this report is the demonstration of the fact that the new waves can propagate slower than the BGM wave. This problem can be very important due to the fact that among the other known SH-SAWs the BGM wave can propagate significantly slower than the corresponding SH bulk acoustic wave. Two new SH-SAWs are analytically and graphically studied in dependence on the electromagnetic constant α. For the graphical study, two (6 mm) composites are used: BaTiO3-CoFe 2 O 4 and PZT-5H-Terfenol-D. For the second composite it is solidly demonstrated that for small values of α, the eighth new SH-SAW cannot exist and its velocity starts with zero at some small threshold value of α rapidly reaching the BGM-wave velocity. This means that a weak magnetoelectric effect can dramatically slow down the speed of either new SH-SAW. As a result, the studied new SH-SAWs can be suitable for creation of new technical devices to sense the magnetoelectric effect. For the analytical study, extreme and inflexion points were evaluated in the velocities' dependencies on the value of the electromagnetic constant α. Keywords Magnetoelectroelastics, Magnetoelectric Effect, New SH-SAW, Bleustein-Gulyaev-Melkumyan Wave A. A. Zakharenko 74

On Discovery of the Twelfth and Thirteenth New Nondispersive SH-SAWs in 6 mm Magnetoelectroelastics

“…Indeed, as soon as α <> 0, the fifth new SH-SAW can propagate. This is similar to the eighth and tenth new SH-SAWs discovered in reference [18,19], respectively, and studied in reference [20]. However, the existence conditions for the latter two new SH-SAWs are more complicated.…”

“…However, the existence conditions for the latter two new SH-SAWs are more complicated. These SH-SAWs cannot propagate in some PEM (composite) solids of class 6 mm [20] and require large enough value of the electromagnetic constant α. Generally, the value of the α is very small for real piezoelectromagnetics that are available today for commercial aims.…”

“…It is also necessary to mention that the dissipation phenomenon can exist at very small values of α 2 /εµ that are smaller than some threshold value (α 2 /εµ) th for the 8th and 10th new SH-SAWs discovered in references [18,19], respectively. Some propagation peculiarities of the 8th and 10th new SH-SAWs were studied in reference [20]. If α 2 /εµ > (α 2 /εµ) th , the 8th and 10th new SH-SAWs can propagate.…”

“…Also, the existence of the dissipation phenomenon with the imaginary propagation velocity at a narrow α-range, 0 < α 2 /εµ < (α 2 /εµ) th , is caused by the corresponding vacuum parameter, ε 0 or µ 0 . Theoretical work [20] also states that the 8th and 10th new SH-SAWs are apt for constitution of technical devices to study (to sense) the magnetoelectric effect. Figure 3 shows the behavior of the normalized velocity V new13 /V tem in dependence on the nondimensional parameter α 2 /εµ for composite materials BaTiO 3 -CoFe 2 O 4 and PZT-5H-Terfenol-D.…”

“…Also, extra four new SH-SAWs were recently discovered [18,19]. Some of the new waves studied [20] can have a dramatic dependence on the ME effect. These four new SH-SAWs must be added to the known seven new SH-SAWs discovered by the author in a 2010 book [21] and three SH-SAWs by Melkumyan introduced in his 2007 paper [22].…”