Abstract

The effect of heat treatment on magnetic rotation in sputtered cobalt films. The films were prepared in a special depositing chamber, the main feature of which was an arrangement for keeping the films cool during the process of sputtering.

Magnetic rotation measurements were made over the wavelength range .6μ to 2.3μ on such cathodically sputtered cobalt films before and after heating for a number of hours at about 300°C in low pressure palladium-pure hydrogen. The result of this heat treatment was to increase several-fold the rotations at 2μ for both the Faraday (transmission) and Kerr (reflection) effects, while towards the visible the change was small.

Conclusions drawn from this are based on the assumption that heat treatment coalesces the granules of which the film is composed into larger units. Then since the magnetic rotation is seen to depend on the size and character of the particles, it should be regarded in this case as a molar rather than molecular or atomic property, the effects being determined by conducting electrons even for wavelengths as short as 1μ.

Experiments on a nickel film and on colloidal iron yielded results in agreement with this conclusion.

© 1924 Optical Society of America

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