Thickness and coupling effects in bilayered multiferroic CoFe_2O_4/Pb(Zr_(0.52)Ti_(0.48))O_3 thin films

摘要

Four CoFe_2O_4/Pb(Zr_(0.52)Ti_(0.48))O_3 (CFO/PZT) bilayered thin films with increasing PZT constituent layer thicknesses have been fabricated in order to investigate the optimized PZT layer thickness and the thickness effect on the magnetic and ferroelectric behaviors of the heterolayered multiferroic thin films. These heterostructured thin films were fabricated via a combined route of spin coating and rf sputtering. Both magnetic CFO and ferroelectric PZT phases were successfully retained in the heterostructured thin film. The improved saturation magnetization (M_s) of the CFO/PZT thin films has been observed and the enhancement increases with increasing PZT layer thickness. Both ferroelectric and dielectric measurements suggest the presence of interfacial space charge polarization arising from the ferroelectric/magnetic interface. Among the multiferroic thin films containing different PZT layer thicknesses fabricated, the thin film that consisted of six PZT constituent layers demonstrated the highest M_s value of 397 emu/cm~3 and the best ferroelectric property with P_r and E_c of 29.91 μC/cm~2 and 138.67 kV/cm, respectively, at 500 kV/cm, together with ε_r and tan δ values of 116.420 and 0.717, respectively, at 100 kHz. Investigation into its magnetoelectric effect demonstrated an α_(E,33) of 238 mV/cm Oe, which was measured by superimposing an ac magnetic field of 5 Oe at 5 kHz onto a dc magnetic field of 4.4 kOe.