3-D Magnetic Orientation Control of Ferromagnetic Film/Guanine Crystal Hybrid Plate

The light reflection intensity from a biogenic guanine crystal that shows strong light scattering on the broadest surface of the crystal can be modulated by the magnetic field switching due to the dynamic motion of magnetic orientation caused by the diamagnetic anisotropy. Magnetic field amplitudes required for magnetic orientation are drastically decreased by hybridizing the guanine crystal with a ferromagnetic thin film, which is one of the important factors for device application from the viewpoint of power consumption and field generation method. In this paper, we present the 3-D magnetic orientation control of the guanine crystal hybridized with the 5 nm thick permalloy film by applying the magnetic field with a three-axis Helmholtz coil. Vertical magnetic field dependences of the tilt angle of (102) plane of the guanine crystal from the substrate for various in-plane magnetic fields are investigated. It is clarified that the hybrid plate can be controlled three-dimensionally with the magnetic field less than several milliteslas by applying the suitable in-plane field. It is shown that the hybrid plate floating under water is transported by the magnetic field gradient using the permanent magnet, which is effective for carrying it to the target position. The 3-D magnetic orientation characteristics of the hybrid plate that shows the similar behavior to the biogenic guanine crystal for the vertical magnetic field are also mentioned.