Magnetic Properties of Thin Nickel Films

Nickel films deposited from a nickel ammonium sulphate solution containing boric acid show decreasing coercive force with decreasing thickness in the range from 140 to 60 mμ. The films are similar to films deposited from the same solution but without boric acid, but are magnetically harder. Nickel films show an ageing effect not found for iron and cobalt. Heating to l00°C accelerates this effect. The effect of tension on the films is studied by measuring at 100°C, in which case the differential expansion of the brass base and the film supplies the tension. The effect is zero for thickness of about 110 mμ and is opposite in sense for thicker and thinner films. This result cannot be explained in terms of the usual effect of tension on bulk nickel