Field-induced diffraction patterns in a magneto-rheological suspension

Fraunhoffer diffraction patterns induced by external magnetic field in a magneto-rheological suspension of micron-sized magnetite particles in a stable kerosene-based magnetite magnetic fluid are studied. It is observed that the patterns significantly change with increase in the field and at a critical field the patterns completely disappears. With further increase in the field it again reappears. Magnetically induced extinction is also observed for this suspension. The extinction exhibits reversal with increase in the field when electric vector of incident light is perpendicular to the direction of the field. A possible explanation of this effect is discussed. (c) 2004 Elsevier B.V. All rights reserved.