MAGNETIC EFFECTS ON THICKNESS OF ADSORBED LAYER IN AQUEOUS-SOLUTIONS EVALUATED DIRECTLY BY ATOMIC-FORCE MICROSCOPE

The short-range interaction force between a mica surface and an AFM pr obe tip in electrolyte solutions was measured by atomic force microsco py (AFM) to directly evaluate the thickness of the adsorbed layer on t he surface, The magnetic effects were estimated by comparing the thick ness in the magnetized solution with that in nonmagnetized solution. I t was found that (i) the magnetic exposure thickens the adsorbed layer on the surface in electrolyte solutions, (ii) the magnetic effects ar e easily destroyed by the external disturbance, (iii) there exists a m emory in the magnetic effects, which remains for at least a day, (iv) the magnetic effects appear mostly in the solutions of structure-disor dering cations, such as Cs+, Rb+, and K+, and (v) the results are cons istent with those obtained in preceding macroscopic experiments. It is hypothesized from these results that the water molecules weekly bound around the structure-disordering ions are quasistabilized and structu red by the magnetic exposure and that the magnetic thickening of the a dsorbed layer is caused by the adsorption of those structured ions on the surface. (C) 1998 Academic Press.