Investigation of the Soret coefficient in magnetic fluids using the Z-scan technique

The generalized thermal lens model formalism, which includes on it the thermodiffusion phenomenon, is used to determine the Soret coefficient (S-T) of a cationic surfacted ferrofluid. The single-beam Z-scan experiment is employed to obtain both the magnitude and sign of ST. Besides ST, the method allows the determination of the parameter partial derivative n/partial derivative I, where n and I are the sample index of refraction and the incident laser beam intensity on the sample. This parameter accounts for the third-order nonlinear optical effects which yield in the sample an instantaneous modification of the index of refraction, proportional to the intensity of the local light. (c) 2004 Elsevier B.V. All rights reserved.