Magnetically directed self-assembly of photonic crystals

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The formation of three-dimensional photonic crystals from magnetic core-shell colloids shall be investigated. Sub-micron sized core-shell particles consisting of layers of Ti02 and Fe304 nanocrystals around a latex core are dried from colloidal suspensions under the steering forces of a magnetic field gradient. This approach allows the study of condensation and structural phase transitions using different field gradients and boundary conditions. Magnetic and optical properties are determined by para- and ferromagnetic resonance and optical spectroscopy. Lithographically pre-patterned silicon substrates are used to stabilize two-dimensional seed layers for the growth of the 3D colloid crystals. Removal of the latex core is possible and magnetically tunable photonic crystal due to magnetostrictive distortions of the colloid crystals may be obtained.