Resistive switching behavior and improved multiferroic properties of Bi0.9Er0.1Fe0.98Co0.02O3/Co1-xMnxFe2O4 bilayered thin films

Bilayered Bi0.9Er0.1Fe0.98Co0.02O3/Co1-xMnxFe2O4 (BEFCO/CMxFO) thin films were deposited by the sol-gel method. Structural variations between the triclinic-P1 and trigonal-R3c:H (two-phase coexistence) phases in the BEFCO layer were observed owing to the trigonal-R-3m:H phase existing in the CMxFO layer. The oxygen vacancy concentrations of the BEFCO/CMxFO bilayered films are reduced by Mn-doping in the bottom CFO layer. The BEFCO/CFO films showed high oxygen vacancy concentrations with a high leakage current. This induced changes of the significant potential barrier at the interface between the BEFCO and CMxFO layers in the processes of electron capture and release. Thus, the BEFCO/CFO film exhibited obvious resistive switching (RS) effect. The high leakage current also caused a fake polarization phenomenon with a blow up of the P-E loop in the BEFCO/CFO films. However, the real and outstanding ferroelectric properties, which resulted from the fewer oxygen vacancies and the 38% triclinic-P1 structure, were obtained in the BEFCO/CM0.3FO films (Pr~156.3 μC cm−2). In addition, the typical capacitance-voltage curve further confirmed its superior ferroelectric performance. The RS effect almost disappeared in the BEFCO/CM0.3FO bilayered films. Moreover, the enhanced ferromagnetic properties (Ms~100.36 emu cm−3, Mr~55.38 emu cm−3) were obtained for the BEFCO/CM0.1FO films, which was attributed to the magnetic properties of BEFCO (a more triclinic-P1 phase and numerous Fe2+ ions), in addition to the CMxFO layer. The introduction of the doped magnetic layer into the bilayered films thus represented a highly effective method for enhancing the multiferroic properties of BFO.