The effects of different Ni/Zn ratios on the magnetoelectric properties of NixZn1-xFe2O4-BiFeO3 composites

Abstract

Bulk samples and thin films of BiFeO3 (BFO)?NixZn1-xFe2O4 (NZFO x=0 3?0 7) composites were prepared by hot-pressing and RF magnetron sputtering respectively One of the aims was to study the effects of different Ni/Zn ratio on the magnetoelectric (ME) property of the BFO?NZFO composites Thin films were grown on the LaNiO3 (LNO) buffered Si substrates by co-sputtering from two individual targets of BFO and NZFO The results showed that the highest ME coefficients were achieved with the BFO?NZFO films of x=0 3 which were measured to be 1531 and 1787 mV/cm?Oe at 10 kHz without and with a DC magnetic bias of 1000 Oe respectively The ME coefficients were measured vertically from the conductive LNO buffer to film surface The x=0 3 composite films also showed the highest magnetization of 788 2 emu/cc For the bulk composites NZFO thin disks were first synthesized by solid state sintering while BFO disks were cold-pressed from the hydrothermal synthesized powders of a pure phase The two disks were then hot-pressed together under the pressure of 4000 kg/cm2 at 200 ?C with silver epoxy painted at the interface The ME coefficients of the bulk BFO?NZFO composites were far smaller than the films which were typically in the order of 10 mV/cm?Oe A part of the reason for the far smaller ME coefficient might be attributed to the inaccurate thickness used for the calculation The effective thickness that had the contribution to the ME coupling might be far smaller than the sample thickness which was typically 0 8 mm compared to the films of 300 nm

Date of Award	2019
Original language	English
Supervisor	Xiao-Ding Qi (Supervisor)