Nanoscale magnetoelectric coupling study in (111)-oriented PZT-Co ferrite multiferroic nanobilayer thin film using piezoresponse force microscopy: Effect of Co ferrite composition

The perfect (111)-oriented PZT/Co(0.)8Fe(2.2)O(4) and PZT/Co0.6Mn0.2Fe2.2O4 bilayer multiferroic thin films were grown on Pt(111)/Si substrate using pulsed laser deposition technique. The PZT/Co0.6Mn0.2Fe2.2O4 bilayer showed higher magnetization and lower coercivity than the PZT/Co0.8Fe2.2O4 bilayer film, which is due to the Mn substitution in the cobalt ferrite layer. The effect of composition of cobalt ferrite underlayer on local magnetoelectric coupling of samples was investigated using piezoresponse force microscopy under external magnetic field, showing magnetically induced evolution of piezoresponse and ferroelectric switching characteristics as a result of interfacially strain transferred from magnetostrictive cobalt ferrite underlayer. The change in piezoresponse amplitude of PZT/Co0.6Mn0.2Fe2.2O4 by applying the magnetic field was higher than that of PZT/Co0.8Fe2.2O4 film and both were significantly higher than that for PZT/CoFe2O4, which has been discussed based on their magnetostriction properties. These results revealed that in comparison to PZT/Co0.8Fe2.2O4, the Mn-substituted bilayer film can be used in lower magnetic fields to reach the same magnetoelectric response making it feasible to the work at lower level of magnetic field in the sensor and actuator devices. (C) 2016 Elsevier B.V. All rights reserved.