Ferroelectric and ferromagnetic nanofibers: synthesis, properties and applications

As first time, ferroelectric (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCTZ), biocompatible (Na0.5K0.5)NbO3 (NKN), and ferromagnetic Y3Fe5O12 (YIG) nanofibers were synthesized by sol-gel assisted electrospining technique. Non-woven, bead-free 100 μm long fiber mat was formed from close-packed nanocrystals after calcination in air at 800°C (BCTZ and NKN) and 1100°C (YIG). BCTZ fibers are 200 nm in width whereas NKN and YIG fibers have smaller 50-100 nm diameter. X-ray diffraction and Raman spectroscopy show that BCTZ and NKN crystallized in tetragonal and rhombohedral polar phases in the vicinity of morphotropic phase boundary. Room temperature ferromagnetism in YIG fibers is indicated by a well formed M-H hysteresis loop with about 70% of remnant magnetization to the saturated value reached at 150 Oe. Broad band microwave spectroscopy revealed strong asymmetry of the shape of ferromagnetic resonance lines that conforms to a three orders of magnitude shape aspect ratio of YIG nanofibers.