Multiferroic Pb(Zr_0.52Ti_0.48)O₃-CoFe₂O₄ Janus-Type Nanofibers and Their Nanoscale Magnetoelectric Coupling

One-dimensional (1D) multiferroic composite nanofibers are known to exhibit enhanced magnetoelectric (ME) coupling compared to their thin-film and bulk counterparts with similar compositions. While measuring their local ME coupling at the nanoscale is essential for understanding multiferroic interactions, it remains challenging due to their complex structure. In this work, multiferroic Pb(Zr_0.52Ti_0.48)O₃-CoFe₂O₄ (PZT-CFO) Janus-type nanofibers were synthesized by electrospinning. This unique structure is expected to provide a more compact and continuous interface between the ferroelectric and ferromagnetic phases compared to core-shell configurations. X-ray diffraction confirmed the coexistence of the perovskite PZT and spinel CFO phases without detectable impurities. The Janus configuration was directly verified by scanning electron microscopy and Kelvin probe force microscopy, which revealed a distinct surface potential contrast between the two halves of a single nanofiber. Magnetic hysteresis loops demonstrated the macroscopic ferromagnetic behavior of the nanofiber assembly. Local magnetoelectric coupling was probed using piezoresponse force microscopy under an applied magnetic field. An enhancement of the intrinsic piezoresponse from 15 pm to 19 pm. was observed upon applying an 8000 Oe magnetic field, providing direct evidence of strain-mediated ME coupling at the nanoscale. Although no ferroelectric domain switching was observed, likely due to the substrate clamping effect, the observed piezoresponse modulation confirms the functional ME interaction. These findings suggest that the Janus nanofibers hold promise for applications in one-dimensional multiferroic devices.