Effect of excitation power on voltage induced local magnetization dynamics in an ultrathin CoFeB film

Abstract

Voltage or electric field induced magnetization dynamics promises low power spintronics devices. For successful operation of some spintronics devices such as magnetic oscillators and magnetization switching devices a clear understanding of nonlinear magnetization dynamics is required. Here, we report a detailed experimental and micromagnetic simulation study about the effect of excitation power on voltage induced local magnetization dynamics in an ultrathin CoFeB film. Experimental results show that the resonance line-width and frequency remains constant, whereas cone angle of the magnetization precession increases linearly with square-root of excitation power below threshold value, known as linear excitation regime. Above threshold power, the dynamics enters into nonlinear regime where resonance line-width monotonically increases and resonance frequency monotonically decreases with increasing excitation power. Simulation results reveal that a strong nonlinear and incoherent magnetization dynamics are observed in our experiment above the threshold power which reduces dynamic magnetic signal by suppressing large cone angle of magnetization precession. Moreover, a significant transfer of spin angular momentum from uniform FMR mode to its degenerate spin waves outside of excitation area further restrict the cone angle of precession within only few degrees in our device. Our results will be very useful to develop all-voltage-controlled spintronics devices.

Towards magnonic devices based on voltage-controlled magnetic anisotropy

“…ΔK S ¼ βE, where ΔK S is the change in iPMA and β is known as magnetoelectric or VCMA coefficient. Several experimental reports show this linear variation of iPMA with electric field [45][46][47] . However, the magnitude and sign of β depend upon several factors.…”

“…There are several important characteristics of VCMA excitation of FMR (VCMA-FMR). One of the most promising and sensitive methods for electrical detection of VCMA-FMR is the homodyne detection technique by using TMR effect 47,62,63 (Fig. 3a).…”

“…The reported value of β is up to few tens of fJ V À1 m À1 for CoFeB/MgO interface 44,47,50 . One of the challenges is to increase the value of β in order to further improve the efficiency of magnonic devices.…”

“…However, the magnitude and sign of β depend upon several factors. For instance, VCMA coefficient and its sign can be same or different for opposite polarity of electric field [46][47][48][49] . Xiang et al reported nonlinear variation of iPMA with electric field for Cr/Fe/MgO heterostructure 42 with a local minima of iPMA at E ¼ þ100mV nm À1 (Fig.…”

Dynamic electromagnonic crystal based on artificial multiferroic heterostructure

“…Therefore, it is enough to apply voltage to the BST slab in one direction that simplifies demands to the DEMC voltage supply. For voltage-controlled magnonic crystals based on electric field controlled perpendicular magnetic anisotropy (PMA) the change in the PMA is a linear function of E [39][40][41] . As a result, the value of PMA can be both increased and reduced.…”