Experimental demonstration of acoustic wave induced magnetization switching in dipole coupled magnetostrictive nanomagnets for ultralow power computing

Abstract

We report nanomagnetic switching with Acoustic Waves (AW)

Static and Dynamic Magnetic Properties of Sputtered Fe–Ga Thin Films

“…A series of new experiments have shown the possibility of strain–mediated switching in Co [17]–[19] and FeGa-alloy based nanomagnets [20]. While transition metal ferromagnets (Fe, Co, Ni) exhibit relatively modest bulk magnetostriction coefficients (∼ 10 −5 ), binary and ternary alloys such as Fe 0.81 Ga 0.19 (Galfenol) and Tb 0.3 Dy 0.7 Fe 2 (Terfenol-D) exhibit magnetostriction coefficients nearly ten times higher for particular stoichiometric compositions [21], [22].…”

Skyrmion motion induced by voltage-controlled in-plane strain gradients

“…8,9 The traditional way to move skyrmions is by spin-polarized currents, [10][11][12][13] but other approaches that do not involve charge currents and the associated Joule heating effects are being explored, such as electric fields, 14,15 spatially variable magnetic fields, 16,17 temperature gradients, 18,19 spin waves, 20 and voltage-controlled anisotropy gradients. [21][22][23][24] Meanwhile, the possibility of controlling magnetic textures using mechanical stress is currently being investigated, with promising results in domain walls 25,26 and skyrmions. [27][28][29][30][31] In particular, there is experimental evidence that skyrmions can be nucleated and annihilated through stress control of the topological phase transition in bulk single crystals, 27,28 whereas simulations indicate that voltage-controlled strain-mediated switching of skyrmions is possible in heterostructures with the interfacial Dzyaloshinskii-Moriya (DM) interaction on top of a piezoelectric (PZ) substrate.…”

Energy-efficient switching of nanomagnets for computing: straintronics and other methodologies

“…If the strain pulse is timed such that the strain is relaxed as soon as the 90 0 rotation is completed, then a residual torque acting on the magnetization due to the strain induced magnetization dynamics continues to rotate the magnetization after the strain is relaxed until a 180 0 rotation is completed and the magnetization has flipped (switched) [30]. Our calculations [31,32] and experiments [33][34][35][36][37] seem to show that strain mediated magnetization control in magnetostrictive nanomagnets (with appropriate scaling) is a very energy-efficient scheme to rotate the magnetization of a nanomagnet. The energy dissipation in a properly scaled multiferroic nanomagnet can be ~ 5 aJ, albeit the rotation speed is relatively slow (~ 1 ns), which makes the energy-delay product ~ 5 10 -27 J-sec.…”

“…[106] earlier. 36 At first glance, this mode of switching may not appear very reliable at room temperature. In the presence of thermal noise and other perturbations, the precessional period varies from cycle to cycle, which means that there is a significant spread in the precessional period.…”

“…We mention acoustic wave clocking (for such functions as Bennett clocking) merely as an enticing prospect, while recognizing that its actual implementation is going to be certainly difficult. 59 While Bennett clocking with acoustic waves faces some hurdles, there are reports of switching the magnetizations of isolated and dipole-coupled nanomagnets with acoustic waves [36,37]. Recent work in this area has been motivated by the realization that "mixed mode" switching of nanomagnets, where both spin transfer torque and stress produced with an acoustic wave are used to switch the magnetization of an elliptical nanomagnet with in-plane anisotropy, can reduce the switching energy dissipation compared to switching with spin transfer torque alone [142,143].…”