Hybrid Magnetodynamical Modes in a Single Magnetostrictive Nanomagnet on a Piezoelectric Substrate Arising from Magnetoelastic Modulation of Precessional Dynamics

Abstract

Magneto-elastic (or "straintronic") switching has emerged as an extremely energy-efficient mechanism for switching the magnetization of magnetostrictive nanomagnets in magnetic memory, logic and non-Boolean circuits. Here, we investigate the ultrafast magneto-dynamics associated with straintronic switching in a single quasi-elliptical magnetostrictive Co nanomagnet deposited on a piezoelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) substrate using time-resolved magneto-optical Kerr effect (TR-MOKE) measurements. The pulsed laser pump beam in the TR-MOKE plays a dual role: it causes precession of the nanomagnet's magnetization about an applied bias magnetic field and it also generates surface acoustic waves (SAWs) in the piezoelectric substrate that produce periodic strains in the magnetostrictive nanomagnet and modulate the precessional dynamics. This modulation gives rise to intriguing hybrid magneto-dynamical modes in the nanomagnet, with rich spin wave texture. The characteristic frequencies of these modes are 5-15 GHz, indicating that strain can affect magnetization in a magnetostrictive nanomagnet in time scales much smaller than 1 ns (~100 ps). This can enable ~10 GHz-range magneto-elastic nanooscillators that are actuated by strain instead of a spin-polarized current, as well as ultrafast magneto-electric generation of spin waves for magnonic logic circuits, holograms, etc.

Generation of charge current from magnetization oscillation via the inverse of voltage-controlled magnetic anisotropy effect

“…Spin-polarized current has been successfully used to manipulate the magnetization ( 1 ). Various physical phenomena based on the coupling of spins to phonons ( 2 , 3 ), orbital angular momentum ( 4 – 6 ), or heat current ( 7 – 9 ) have been observed recently, which has led to novel possibilities of switching the magnetization direction. Control of ferromagnetism by electric field is quite attractive ( 10 , 11 ) as it can lead to ultralow-power writing methods for magnetic memories.…”

Electric-field-assisted non-volatile magnetic switching in a magnetoelectronic hybrid structure

“…They demonstrated an ultralow writing energy on the order of fJ/bit using strain-mediated magnetoelectric coupling in an MTJ/FE hybrid. Bandyopadhyay et al (Roy et al, 2011;Mondal et al, 2018) further showed that the switching energy can be down to a scale of $ aJ/bit in a single nano-magnet on a piezoelectric (PE) substrate. Recently, Carman et al (Wang et al, 2018b) conceptualized an MTJ/FE structure which is controlled by SOT and ME effect.…”

“…Bandyopadhyay et al. ( Roy et al., 2011 ; Mondal et al., 2018 ) further showed that the switching energy can be down to a scale of ∼ aJ/bit in a single nano-magnet on a piezoelectric (PE) substrate. Recently, Carman et al.…”

Surface acoustic wave induced modulation of tunneling magnetoresistance in magnetic tunnel junctions

“…SAW of ~100 MHz frequency has been used to actuate extreme sub-wavelength magneto-elastic antennas consisting of magnetostrictive nanomagnets delineated on a piezoelectric substrate [30]. Optically generated SAW of several GHz frequency has been utilized to cause magnetization precession and generation of confined spin waves in isolated magnetic nanodots [31] as well as traveling spin waves in arrays of magnetic nanodots [32]. SAW-mediated picosecond magnetization switching has also been predicted [33][34][35].…”