Designing ferroelectric/ferromagnetic composite with giant self-biased magnetoelectric effect

We report a simple and effective method to obtain the magnetoelectric (ME) effect at zero magnetic bias field (H-DC = 0), i.e., the self-biased ME (SME) effect, using an ME laminate composite clamped at its center with its free ends loaded with magnetic tip masses. The method exploits the shifting of the magnetic hysteresis loop of the ferromagnetic (FM) layer of the laminate induced by a preapplied magnetic field (H-p) along the longitudinal direction. The optimum magnetic-field strength corresponding to the maximum of the ME voltage coefficient (alpha(ME)) vs H-DC curve was calculated using equations derived from correlations of magnetic coefficients. In experiments involving the laminate with an FM/ferroelectric/FM symmetrical structure, the strength of H-p was tuned to the optimum value, shifting the alpha(ME) vs H-DC curve along the H-DC axis enough to obtain the maximum alpha(ME) at H-DC = 0 (alpha(SME)). To further enhance alpha(SME), an asymmetric configuration of the laminate was designed using two different FM materials having piezomagnetic coefficients with opposite signs. The ME laminate with the asymmetrical structure exhibited a large alpha(SME) of 55.7 V cm(-1) Oe(-1) at its bending resonance frequency.