Switching processes in thin ferromagnetic film memory elements

The switching properties of small, rectangular areas of thin ferromagnetic films, relevant to their utilization as memory elements in digital computers, are discussed. An attempt is made to derive the switching properties theoretically by superposition of the calculated demagnetizing field effects upon the known intrinsic film properties. Experiments performed using homogeneous quasi-static applied fields show good agreement with the theory. In the case of high easy direction applied fields the complexity of the magnetization distributions necessitates a number of simplifying assumptions in the theoretical treatment, and here the agreement is poorer. The treatment is sufficiently accurate to yield relationships between the intrinsic film properties, the dimension of the element, and the available output flux. In practical configurations the element is switched by inhomogeneous fields produced by fast current pulses in strip lines, and its state is ascertained by the observation of an EMF induced by the rotating magnetization. The differences between the configuration observed here and the practical one are discussed.