Intense light scattering by cooperative relaxation of magnetically-aligned organic crystal particles

• Main Authors: K. Baba, M. Iwasaka
• Format: Article
• Language: English
• Published: AIP Publishing LLC 2019-03-01
• Series: AIP Advances
• Online Access: http://dx.doi.org/10.1063/1.5079678

Previous studies of biologically mineralized crystals made of iron have focused on their magnetic properties, including strong magnetism and para magnetism, and many useful applications have been developed. Some studies have focused on organic crystals or crystals with diamagnetism, and have proven that utilizing magnetic fields of more than 0.5 T results in a magnetically-induced rotation of the crystal particles. The rotation of an appropriately shaped crystal particle can be detected by light reflection. In the present study, we demonstrate a newly discovered phenomenon associated with organic crystal particles in water. A cooperative light reflection phenomenon is observed when the micro-particles floating in water are rotated together. The organic crystal particles, made of guanine in a platelet-like shape of micrometer length, cause a cooperative light reflection pattern during magnetic field sweeps of up to 5 Tesla (T). This cooperative light reflection appears as peaks in the intensity of the reflected light. When the magnetic field is increased at a sweep rate of +1 T per minute, two peaks are detected at 0.5 T and at ∼1.5 T. After reaching 5 T, the reflected light is continuously measured until the magnetic field returns to 0 T. In over 10 minutes of magnetic field exposure, a final peak is frequently detected as a maximum intensity peak. The intensity enhancement is twice the randomly reflected light intensity in this maximum case. A model explaining this magnetically-controlled optical phenomenon in a group of platelet-like guanine particles is proposed.