Charge mediated room temperature magnetoelectric coupling in Zn1−xSmxO/BaTiO3 bilayer thin film

Abstract

We present a room-temperature magnetoelectrically coupled bilayer thin film multiferroic system (BTS) ‘Zn1−xSmxO/BaTiO3 (where x = 0.02 and 0.04)’ grown on a SrTiO3 (100) substrate. The thin film layers are polycrystalline and continuous with an average roughness of 3.2 nm. At room temperature, the BTSs with x = 0.02 (BTS2) and x = 0.04 (BTS4) are ferromagnetic with a saturation magnetic moment (Ms) of 5.1 memu and 8.6 memu respectively, while the latter shows a paramagnetic trace. Both BTS2 and BTS4 are ferroelectric at room temperature with a saturation polarization (Ps) of 12.51 μC cm−2 and 6.75 μC cm−2, respectively. The coercive (electric) field required to polarize BTSs increases as a function of x (25.2 kV cm−1 for BTS2 and 62.3 kV cm−1 for BTS4). The change in degree of polarization/magnetization (domain contrast of the piezoresponse/magnetic force microscopy images), permittivity and resistance, as a function of external magnetic/electric field, directly suggests that the Zn0.98Sm0.02O/BaTiO3 BTS is magnetoelectrically coupled at room temperature.