No abstract

In general, magnetic properties of bulk magnetic materials are independent of the humidity of the environment. To obtain a magnetic material that has humidity-sensitive characteristics, water vapour must penetrate the lattice and act on spin sites. Nanoporous materials composed of metal-assembled complexes may be expected to display some humidity response because materials in this category can show functionalities such as gas storage and molecular recognition. Here, we demonstrate humidity-induced reversible variations in the magnetic properties of cyano-bridged cobalt(II)-manganese(II)-chromium(III) metal assemblies. The observed magnetic humidity response is due to adsorption and desorption of a ligand water molecule on the cobalt ion, which changes cobalt (II) between a 6- and 4-fold coordination geometry and switches the magnetic interaction between ferromagnetic coupling and antiferromagnetic coupling.

The magneto-optical (MO) Faraday effect of one-dimensional photonic crystals (1D-PCs) composed of Bi-substituted yttrium–iron–garnet films and dielectric films such as SiO2 and TiO2 films were studied theoretically. Because of considerable localization of light, these media exhibit a very large MO effect. For instance, when the film structure is chosen to be appropriate for supporting the localization of light, the 1D-PC films can possess a huge Faraday rotation angle reaching to −28 deg/μm at λ=1.15 μm. The analysis reveals that the MO characteristics of the 1D-PC films are almost governed by the degree of localization of light, which can be controlled by varying the number of reflection layers in the films.

Two types of one-dimensional photonic crystals composed of magnetic and dielectric materials (magnetophotonic crystals) driven, respectively, by Kerr (reflection) and Faraday (transmission) modes were constructed. Their optical and magneto-optical (MO) properties were studied in detail to confirm our theoretical results showing the large Kerr and Faraday effects of the media originating in the localization of light. For the Kerr-mode operation, films with (SiO2/SiN)×k/Co/(SiN/SiO2)×k (k: number of layers) structures were fabricated, while for the Faraday-mode operation, films with (SiO2/Ta2O5)×k/Bi:DyIG/(Ta2O5/SiO2)×k structures were formed. Excellent agreement between the theoretical and experimental results was obtained, where large enhancement in both Kerr and Faraday rotations appeared originating in the localization of light in the vicinity of the magnetic layers. Since the localized state of light can be controlled artificially, the one-dimensional magnetophotonic crystals will impact for various MO applications.

No abstract