Magnetic fungal colonies on silicon: a nanoscale diffusion process and evidence of thermal capillary waves

Fungal colonies exhibit complex growth patterns depending on the environment. We report the formation of magnetic domains within fungal cells due to the growth of colonies in iron sulfate solution. We find that the initial growth of these colonies on silicon can be described by a roughness exponent of ~0.55 while annealed induced self-assembly has a roughness exponent of ~0.80. The growth mode is consistent with a quenched growth model. We also find high temperature (>600 °C) annealing induced colony parts to form oriented nanostructures with higher saturation magnetization. Using atomic force microscopy we show evidence of thermally induced capillary waves on island surfaces with a van der Waals cutoff wavevector of the order of 10−2 A−1.