Room temperature multiferroic properties of electrospun gallium ferrite nanofibers

Gallium ferrite (GaFeO₃) is a promising multiferroic material for multifunctional device applications. Compared with bulk and thin film materials, nanofibers are possible to magnify the magnetostriction or piezoelectric effect due to their large length–diameter ratio, thus improving the performance of the material. In this work, Ga_xFe_2 – xO₃ (GFO) nanofibers have been synthesized by sol-gel based electrospinning. With the increasing Fe ion content, the room-temperature antiferromagnetic to ferromagnetic transition of GFO nanofibers has been confirmed by magnetic hysteresis loops; and the corresponding temperature dependent magnetization curves show that the ferromagnetic–paramagnetic transition temperature (T_c) is above room temperature and increases from around 292 K to above 400 K. Ferroelectricity of GFO nanofibers has been confirmed by second harmonic generation and piezoresponse force microscopy. Magnetoelectric (ME) coupling has been further measured by dual amplitude resonance tracking piezoresponse force microscopy and sequential excitation piezoresponse force microscopy under an in-plane external magnetic field. The newly developed SE-PFM method reduces the crosstalk of morphology, confirming that no obvious intrinsic ME coupling appears in the GFO nanofibers.