Magneto-elastic switching of magnetostrictive nanomagnets with in-plane anisotropy: the effect of material defects

Abstract

We theoretically study the effect of a material defect (material void) on switching errors associated with magneto-elastic switching of magnetization in elliptical magnetostrictive nanomagnets having in-plane magnetic anisotropy. We find that the error probability increases significantly in the presence of the defect, indicating that magneto-elastic switching is particularly vulnerable to material imperfections. Curiously, there is a critical stress value that gives the lowest error probability in both defect-free and defective nanomagnets. The critical stress is much higher in defective nanomagnets than in defect-free ones. Since it is more difficult to generate the critical stress in small nanomagnets than in large nanomagnets (having the same energy barrier for thermal stability), it would be a challenge to downscale magneto-elastically switched nanomagnets in memory and other applications where reliable switching is required. This is likely to be further exacerbated by the presence of defects.

Magnetization switching in bistable nanomagnets by picosecond pulses of surface acoustic waves

“…The ∼ 10 −4 SAW-induced switching threshold for elliptical Ni nanomagnets appears to be significantly lower as compared to highly magnetostrictive thin films of Terfenol-D switchable by ultrashort longitudinal acoustic pulses with amplitudes ∼ 10 −2 propagating in the direction perpendicular to the surface [22]. This observation may seem surprising because of the ∼ 20 times larger magnetostriction coefficient in Terfenol-D [44]. However, the much longer ∼ 300 ps duration of the SAW pulses as compared to Ref.…”

“…The most critical assumption of the present study, i.e. the single-domain magnetic ground state of elliptic nanomagnets, depends on its dimensions and exchange stiffness [48,49] as well as the presence of nano-scale material defects [44]. Therefore, the experimental realization of the proposed SAW-induced magnetic recording will ultimately involve investigations of elliptical nanomagnets with different aspect ratios and dimensions.…”

Strain‐Induced Interlayer Parallel‐to‐Antiparallel Magnetic Transitions of Twisted Bilayers

“…It should be noted that the existence of possible structural defects like voids and impurities may hinder the strain‐induced magnetic switching. [ 53–55 ] For example, we found that after adding a cylindrical void with a diameter larger than 10nm to the upper magnetic layer, the bilayer system turns into a multidomain state with stripe domains upon application of a strain pulse ( ε xx , ε yy ) = (0.1%, −0.1%) (i.e., the condition for a parallel‐to‐antiparallel transition in a perfect sample), as shown in Figure . This would cause a failure of the strain‐induced transition.…”

Straintronics: Digital and Analog Electronics With Strain-Switched Nanomagnets

“…It has been observed both experimentally [31,33] and theoretically [34,35] that strain, albeit energy-efficient, does not switch nanomagnets reliably, especially real nanomagnets that contain defects. This is the most serious drawback of magneto-elastic switching which is at the heart of straintronics.…”