Tuning magnetoelectric effect in Pb(1-x)SrxTiO3/CoFe2O4 multiferroic nanocomposites by varying Sr content

Effect of chemical compositions in ferroelectric phase on magnetoelectric (ME) coupling is investigated for (3-1) multiferroic Pb(1-x)SrxTiO3/CoFe2O4 nanocomposites, via phase field model. The Sr content in ferroelectric phase varies in a wide range of 0 <= x <= 0.4. Stripe polarization domain structure is stably formed in the ferroelectric matrix, while rectilinear magnetization domain appears in each ferromagnetic nanowire. Average sizes of polarization domains strongly depend on the Sr content in the ferroelectric matrix. The magnitude of polarization in the ferroelectric matrix monotonically decreases with increasing Sr content. Interestingly, the ME coupling of the multiferroic nanocomposites depends non-monotonically on the Sr content. In particular, the ME coefficient increases with the Sr content x < 0.15 and decreases with x > 0.15. The largest ME coefficient is obtained in the multiferroic nanocomposite with x = 0.15. On the other hand, we show that the ME coupling is dependent of both the density of polarization domain walls and elastic energy of the nanocomposites. Importantly, as the Sr content increases, the density of polarization domain walls and elastic energy vary oppositely, which results in the non-monotonic change of ME coupling. The change of ME coupling with the Sr content is governed by the increase of elastic energy as x < 0.15, but dominated by the decrease of domain wall density as X > 0.15. The obtained results suggest an optimized range of chemical compositions in the ferroelectric matrix of multiferroic nanocomposites to obtain a high ME coupling.