Temperature dependence of magnetoelectric effect in Bi3.15Nd0.85Ti3O12–La0.7Ca0.3MnO3 multiferroic composite films buffered by a LaNiO3 layer

Abstract

Multiferroic composite thin films were fabricated based on ferroelectric (FE) Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) and ferromagnetic (FM) La_0.7Ca_0.3MnO₃ (LCMO) parents with different growth sequences of BNT–LCMO/LNO/STO (BL) and LCMO–BNT/LNO/STO (LB). Ferroelectric behaviour along with remnant polarization (2P_r) of 50 μC cm² and 40 μC cm² at room temperature, saturated magnetization values around 206 emu cm⁻³ and 192 emu cm⁻³ at 100 K were measured for BL and LB composite films, respectively. The temperature dependence of the magnetoelectric (ME) coupling effect was investigated and the ME voltage coefficients of 63 mV cm⁻¹ Oe⁻¹ and 60 mV cm⁻¹ Oe⁻¹ at 100 K were respectively obtained for the BL and LB films. The results show that the composite films exhibit both good ferroelectric and ferromagnetic properties, as well as a substantial ME effect. Moreover, it is demonstrated that the layer sequences and temperature have significant impacts on the magnetoelectric coupling behaviour of these double-layered thin films, which is very likely caused by the magnetic–mechanical–electric interaction, substrate clamping and interface coupling.