The resistivity of conducting ferromagnetic liquids containing iron particles in mercury

The resistivity of magnetic fluids consisting of 40A diameter iron particles in mercury has been measured between 77K and 300K. The resistivity decreases for iron particle concentrations above 10¹⁷cm^-1(equivalent to 0.2 at % Fe). If sufficient tin is added to the fluid to form a monolayer coating about the iron only, the resistivity increases for increasing iron particle concentrations above 10¹⁷cm^-3. This difference in behaviour is interpreted in terms of electron scattering due to the existence of charge layers at the particle/mercury carrier interface. The behaviour of the resistivity at constant iron particle concentrations has been studied as a function of tin concentration and is shown to be dependent upon the spatial location of the tin. A time dependant resistivity is observed when the quantity of tin present exceeds the amount required to form a monolayer coating on the iron. The resistivity of the tin coated iron particle fluid is greater than that of pure mercury, at the same temperature, except in the region of the solid to liquid phase transition. In this region a linear change in the resistivity of 3.7 μΩ K^-1is observed.