Theory of single-current domain propagation circuits

Single-current propagation circuits cause circular magnetic domains in a uniaxial ferrimagnetic wafer to move continuously by properly combining dynamic and static forces which vary periodically with distance. The dynamic force is due to a current and varies periodically with time at a frequencyf. The static force has a spatial period one-half the period of the dynamic force. The static force may be produced by a periodic array of Permalloy elements or by a periodic modulation of wafer thickness. The general principle is discussed and a simple mathematical model is used to indicate the optimum amplitude and phase of the static force relative to the dynamic force. Single-current propagation circuits 1] cause circular magnetic domains in a uniaxial ferrimagnetic wafer to move continuously by properly combining dynamic and static forces which vary periodically with distance and have an average value of zero. The dynamic force is due to a current and varies periodically with time at a frequencyf. The second is static and has a spatial period one-half the period of the dynamic force. The static force may be produced by a periodic array of Permalloy elements 2], 3] or by a periodic modulation of wafer thickness 4]. The general principle is outlined in Figs. 1 and 2.