Tailored Magnetic and Magnetoelectric Responses of Polymer-Based Composites

Abstract

The manipulation of electric ordering with applied magnetic fields has been realized on magnetoelectric (ME) materials; however, their ME switching is often accompanied by significant hysteresis and coercivity that represents for some applications a severe weakness. To overcome this obstacle, this work focuses on the development of a new type of ME polymer nanocomposites that exhibits a tailored ME response at room temperature. The multiferroic nanocomposites are based on three different ferrite nanoparticles, Zn0.2Mn0.8Fe2O4 (ZMFO), CoFe2O4 (CFO) and Fe3O4 (FO), dispersed in a piezoelectric copolymer poly(vinylindene fluoride-trifluoroethylene) (P(VDF-TrFE)) matrix. No substantial differences were detected in the time-stable piezoelectric response of the composites (∼-28 pC·N(1-)) with distinct ferrite fillers and for the same ferrite content of 10 wt %. Magnetic hysteresis loops from pure ferrite nanopowders showed different magnetic responses. ME results of the nanocomposite films with 10 wt % ferrite content revealed that the ME induced voltage increases with increasing dc magnetic field until a maximum of 6.5 mV·cm(-1)·Oe(1-), at an optimum magnetic field of 0.26 T, and 0.8 mV·cm(-1)·Oe(1-), at an optimum magnetic field of 0.15 T, for the CFO/P(VDF-TrFE) and FO/P(VDF-TrFE) composites, respectively. In contrast, the ME response of ZMFO/P(VDF-TrFE) exposed no hysteresis and high dependence on the ZMFO filler content. Possible innovative applications such as memories and information storage, signal processing, and ME sensors and oscillators have been addressed for such ferrite/PVDF nanocomposites.

Flexible Magnetoelectric Nanocomposites with Tunable Properties

“…Mostly, ME nanocomposites have utilized magnetostrictive spherical nanoparticles. [11][12][13][14] An anisotropic ME nanocomposite based on δ-FeO(OH) nanosheets was recently reported. The ME voltage coeffi cient was 0.4 mV(cmOe) −1 arising from magnetic rotation of the sheets rather than the magnetostriction effect.…”

“…Fe, Ni, and highly magnetostrictive Fe-Ga (Galfenol) alloys are studied as fi ller materials, which possess magnetostriction constants of 20, 40, and 300 ppm, respectively. [14][15][16][17] While Fe and Ni NWs have been studied in detail before, [ 18,19 ] only little is known about the fabrication and properties of Galfenol NWs. [ 20,21 ] Fe, Ni, and Galfenol NWs with diameter of 50 nm and length of 5 µm were prepared utilizing a DC electrodeposition technique inside of aluminum oxide membranes (AOM).…”

“…The selected area electron diffraction pattern confi rms the single crystallinity of the Galfenol NWs (Figure 1 c). Figure 1 d shows the energydispersive X-ray composition spectrum of Galfenol NWs, which were found to be Fe 86 Ga 14 . This composition is within the range of the highly magnetostrictive alloy and should provide a magnetostriction of around 200 ppm.…”

“…The obtained results are in agreement with those reported for nanocomposites using spherical nanoparticles or carbon nanotubes. [ 8,11,14,26,27 ] At a higher concentration, the piezoelectric coeffi cient decreases as the polymerization starts becoming compromised.…”

“…This value is the highest ever reported for magnetic-based polymer nanocomposites measured by the same method. [ 11,12,14,26 ] One important observation for the Ni NWs is that the measured ME voltage decreases, when applying a positive magnetic bias fi eld, unlike Fe or Galfenol NWs. This behavior can be attributed to the negative magnetostriction of Ni, whereas Fe and Galfenol both possess positive magnetostriction (Figure 1 f).…”