CHAPTER 10: Chemical Routes to Fabricate Three‐Dimensional Magnetophotonic Crystals

We provide an overview of the methodologies essayed by us to achieve three‐dimensional magnetophotonic crystals (3D‐MPCs) with enhanced magneto‐optic responses. The crystals were fabricated by infiltrating direct and inverse opals with magnetic nanoparticles either via opal impregnation in liquid colloidal dispersions of ex situ synthesized nanoparticles or in situ nanoparticle formation exploiting a microwave‐assisted sol‐gel route. Using these approaches, we have realized 3D‐MPCs with high‐quality, long‐range structural order (at least in the order of a few mm²) and high magnetic filling ratios up to above 30%. As a consequence, the resulting 3D‐MPCs exhibit a large magnetophotonic imprint in their magneto‐optic spectral responses, achieving large signals at the stop‐band edge frequencies. These results offer a promising route towards novel materials for photonic applications, in which the optical spectral responses can be tailored at will. Additionally, the versatility of the microwave‐assisted chemistry to achieve high‐quality conformal coatings of intricate 3D structures for applications that could go beyond photonics is demonstrated.