Lead-free BLTO/NMFO magnetoelectric composite films prepared by the sol-gel method

The lead-free ferroelectric films of Bi_4?xLa_xTi₃O₁₂(BLTO) and ferromagnetic films of Ni_1?xMn_xFe₂O₄(NMFO) were prepared on Pt/Ti/SiO₂/Si substrate by means of the sol-gel and spin-coating method. The lead-free magnetoelectric composite films with the structure of Bi_3.4La_0.6Ti₃O₁₂/Ni_0.7Mn_0.3Fe₂O₄/substrate (BN) and Ni_0.7Mn_0.3Fe₂O₄/Bi_3.4La_0.6Ti₃O₁₂/ substrate (NB) were also deposited on Pt/Ti/SiO₂/Si substrate. The X-ray diffraction results show that two composite films possess BLTO and NMFO phases without any intermediate phase. The SEM images show that two composite films exhibit layered structure, clear interface and no transition layer between BLTO and NMFO films. Two composite films exhibit both good ferromagnetic and ferroelectric properties, as well as magnetoelectric coupling effect. The deposition sequence of ferroelectric and ferromagnetic films in the composite films has significant influence on the ferroelectric, ferromagnetic and magnetoelectric coupling properties of the composite films. The values of magnetoelectric voltage coefficient of the BN composite films are higher than those of the NB composite films at any fixed H_bias.