Monolithic Magneto-Optical Nanocomposites of Barium Hexaferrite Platelets in PMMA

Abstract

The incorporation of magnetic barium hexaferrite nanoparticles in a transparent polymer matrix of poly(methyl methacrylate) (PMMA) is reported for the first time. The barium hexaferrite nanoplatelets doped with Sc3+, i.e., BaSc0.5Fe11.5O12 (BaHF), having diameters in the range 20 to 130 nm and thicknesses of approximately 5 nm, are synthesized hydrothermally and stabilized in 1-butanol with dodecylbenzenesulfonic acid. This method enables the preparation of monolithic nanocomposites by admixing the BaHF suspension into a liquid monomer, followed by in-situ, bulk free-radical polymerization. The PMMA retains its transparency for loadings of BaHF nanoparticles up to 0.27 wt.%, meaning that magnetically and optically anisotropic, monolithic nanocomposites can be synthesized when the polymerization is carried out in a magnetic field. The excellent dispersion of the magnetic nanoparticles, coupled with a reasonable control over the magnetic properties achieved in this investigation, is encouraging for the magneto-optical applications of these materials.

Novel Ba-hexaferrite structural variations stabilized on the nanoscale as building blocks for epitaxial bi-magnetic hard/soft sandwiched maghemite/hexaferrite/maghemite nanoplatelets with out-of-plane easy axis and enhanced magnetization

“…Barium hexaferrite (BaFe12O19, BHF) nanoplatelets are a classic example of this type of magnetic structure. 1,16 The BHF crystalizes in a magnetoplumbite structure that can be represented as a hexagonal close-packed stacking of oxygen and barium ions with smaller iron ions positioned at the interstitial sites. The structure can be subdivided into two alternating structural blocks stacked along the c-direction: a hexagonal "R" block ((BaFe6O11) 2-) and a cubic "S" block ((Fe6O8) 2+ ) 17,18 (Fig.…”

“…15 This has led to the use of BFH in diverse applications such as ferromagnetic liquid crystals 3,22 and magneto-optical composites. 1 These applications of hard-magnetic nanoplatelets are very encouraging; however, they also revealed that a further improvement in their MS is necessary. An alternative approach to enhance MS in hard-magnetic materials is the exchange coupling low-MS materials (e.g., BHF) with high-MS softmagnetic materials.…”

Preparation of Barium-Hexaferrite/Gold Janus Nanoplatelets Using the Pickering Emulsion Method

“…Figure 9 shows the UV-vis spectra of the NPLs-Si, gold, and Janus NPL particles prepared in this work and dispersed in water. NPLs-Si (Figure 9a) show a broad absorption below 600 nm, which is the strongest at 300-400 nm and originates from the core BHF NPLs [66]. The Au nanoparticles show typical absorption at around 530 nm due to the surface plasmon resonance (Figure 9b) [67].…”

Theoretical study of alignment dynamics of magnetic oblate spheroids in rotating magnetic fields

“…5 Inspired by the anisotropic architectures of the natural materials, people are committed to developing new materials that contain aligned particles. [6][7][8][9] These materials can exhibit enhanced magnetic, mechanical, optical, and diffusive (heat and mass) properties. For example, soft magnetic composites, consisting of magnetic particles embedded in an insulating matrix, have great potential for a variety of breakthrough applications, including magneto-optics, 10 biological tissue scaffolds, 11,12 drug targeting, 13 and high-frequency applications such as microwave absorption, electromagnetic shielding, 14 inductors, and antennae.…”