Techniques for measuring small changes in the orientation of the easy axis in permalloy films

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Abstract
It is well known that the orientation of the easy axis in permalloy can be affected by annealing. The need in our research for detailed information of the behavior of the easy-axis orientation in the temperature range from room temperature to 100 °C and the absence of measurement techniques to derive this information, led to the development of two new measurement techniques: (1) an adapted version of the Crowther method for measuring dispersion in easy-axis orientation combined with the optical Kerr technique and (2) a new measurement technique for determining the orientation of the easy axis combined with a galvanomagnetic method for determining magnetization direction. Both methods give detailed information on the behavior of the easy-axis orientation as a function of temperature. The resolution of both methods is 0.01° and may be increased, especially for the optical method. The optical method imposes few restrictions on film geometry and may be used, e.g., during a fabrication process. The easy-axis behavior can be observed locally. The galvanomagnetic technique requires four electrical contacts on the film. The easy-axis behavior is averaged over the total current-carrying area. This method can be used for observing the behavior of the easy axis in encapsulated devices.