Thin-Film Polymer Nanocomposites for Multiferroic Applications

Abstract

Polymeric nanocomposite thin films of magnetic nanoparticles blended with the ferroelectric polymer poly-(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) are promising candidates for multiferroic applications. To date, only thick-film multiferroic nanocomposites have been reported. Fabrication of nanocomposite thin films along with the study of the ferroic properties with magnetic nanoparticle loading is crucial for the realization of functional devices. However, systematic studies, and in particular the dynamic of ferroelectric polarization switching and a solid understanding of the microstructure formation in thin films, are still missing. Here, we present solution-processed P(VDF-TrFE):magnetic nanoparticle thin films for multiferroic applications, wherein the ferroic properties, polarization switching dynamic, and the microstructure formation are studied as a function of nanoparticle loading. Our results demonstrate that as the nanoparticle loading increases, the ferroelectric polarization of the nanocomposite decreases and the saturation magnetization increases. Moreover, the presence of the nanoparticles substantially increases the polarization switching time and shifts the switching mechanism to one-dimensional growth. The P(VDF-TrFE):magnetic nanoparticle solution phase separates upon film casting. The crystalline regions of P(VDF-TrFE) are pure. The amorphous regions accommodate the nanoparticles. The phase separation leads to agglomerated nanoparticles at higher loadings, and eventually stratified vertical phases occur. The insight gained from the study of thin-film microstructure would help to optimize the performance of the nanocomposite for multiferroic applications and can be used for better understanding of the polymer:nanoparticle nanocomposites for energy storage and memory applications.

Solution-processed transparent ferroelectric nylon thin films

“…The simple synthesis and tunability of the chemical structure of nylons can now be fully exploited toward the optimization of the ferroelectric properties. The availability, ease of synthesis, and price advantage of nylons compared to ferroelectric fluoropolymers would allow upscaling of low-cost flexible thin films for the envisioned applications of ferroelectric polymers in microelectronics ( 30 ), memories ( 31 , 32 ), and energy harvesting ( 33 ).…”

Impact of Stoichiometry and Size on the Magnetic Properties of Cobalt Ferrite Nanoparticles

“…With the increasing amount of data produced every day, we rely progressively on data storage technologies for digital archiving. Magnetic tapes, particularly when dealing with large amounts of data, have remained as a viable and economical technology for digital archives because of their lower cost per bit and long-term stability. − Achieving high recording density in a tape requires the use of nanomagnets that show ferri/ferromagnetic behavior to block the spin orientation in one direction. − The magnetic properties of the ferrites (Fe 3 O 4 or Fe 2 O 3 ), the conventional materials used in tapes, change upon nanosizing. − Iron oxide nanoparticles (NPs) are usually composed of both Fe 3 O 4 and Fe 2 O 3 phases, which become superparamagnetic or weakly ferro/ferrimagnetic as the NP size is reduced below a critical value . The critical size depends on the composition of the NPs.…”

“…Metal oxide NPs with a large magnetocrystalline anisotropy, such as cobalt ferrite (Co x Fe 3−x O 4 ) 6,13,14,17,18 nanoparticles, are particularly attractive candidates for nanomagnets because of their high coercivity, Curie temperature, and remanent magnetization, good physical and chemical stability, excellent corrosion resistance, and ease of synthesis. 1,11,19−21 The magnetic properties of cobalt ferrite NPs can be finely tuned by changing the cobalt content or the size of the NPs.…”

“…Metal oxide NPs with a large magnetocrystalline anisotropy, such as cobalt ferrite (Co x Fe 3– x O 4 ) ,,,, nanoparticles, are particularly attractive candidates for nanomagnets because of their high coercivity, Curie temperature, and remanent magnetization, good physical and chemical stability, excellent corrosion resistance, and ease of synthesis. ,,− The magnetic properties of cobalt ferrite NPs can be finely tuned by changing the cobalt content or the size of the NPs. ,,,− Moreover, the synthesis of cobalt ferrite NPs is more cost-effective in comparison with those of other ferrimagnet NPs such as FePt, SmCo, and NdFeB. Cobalt ferrites are also relevant in other fields of application such as biomedicine, magnetic hyperthermia, spintronics, magnetic resonance imaging (MRI), catalysts, and sensors. ,,,− For the aforementioned applications, a detailed systematic study of the magnetic properties of the Co x Fe 3– x O 4 NPs as functions of the cobalt stoichiometry ( x ) and the size of the NPs is required in order to achieve nanomagnets with stable remanent magnetization at room temperature, high coercivity, and large magnetocrytalline anisotropy.…”

One-Dimensional Polarization Dynamics in Ferroelectric Polymers

“…Ferroelectric poly­(vinyleden difluoride) (PVDF) has been suggested for a myriad of applications in microelectronic devices, ranging from energy generation and storage to memory devices. , PVDF exists in five crystalline phases: α-, β-, δ-, ϒ-, and ε-, of which the α-phase is not ferroelectric, and the β- and δ-phases show stable ferroelectric behavior. − Fabrication of ferroelectric PVDF thin films, as required for microelectronic applications, − is challenging because solution-processed PVDF typically crystallizes in a centrosymmetric nonpolar α-phase, as shown Figure a …”