Observation of clear magnetization and polarization reversal by local electric field in BiFeO₃-based multiferroic thin film with using metallic MFM tip with optimized magnetization

The induced magnetic and electric domain structures by applying local electric field of (Bi
0.4
La
0.6
)(Fe
0.7
Co
0.3
)O
3
multiferroic thin film (saturation magnetization ($M_{\mathrm{s}}$) of 75 emu/cm
³
, film thickness of 260 nm) fabricated using pulsed DC reactive sputtering technique were observed by magnetic force microscopy (MFM) and electric force microscopy (EFM). To observe clear induced domain structures, metallic and magnetic Co-Cr-Pt (film thickness of 30 nm) coated MFM tips with various $M_{\mathrm{s}}$ (500,700,900emu/cm
³
) were used. With increasing the $M_{\mathrm{s}}$ of Co-Cr-Pt, MFM phase signal increased, but EFM phase signal decreased. The reason of decrease of EFM phase signal was that EFM signal included not only electric force but also magnetic force. As the results, the large MFM and EFM phase signal and clear domain images were obtained by using Co-Cr-Pt coated MFM tips with the saturation magnetization of 700 emu/cm
³
.