Quenching of coercive force in bubble films by domain wall restoring forces

Abstract

A mechanism is proposed to account for the disparity between coercive force in bubble domain films as measured by hysteresis techniques, which employ an ac-bias field component to move the wall, from that measured in pulsed bubble propagation experiments. In the proposed mechanism the magnetic restoring forces, that resist coercivity produced distortions of the wall pattern, greatly reduce the time average lag of the wall position caused by coercivity, to the extent that the restoring forces dominate the actual or true coercive force. The coercive force, measured by the hysteresis method, is proportional to the time average hysteresis lag and is thus reduced or quenched by these restoring forces. In bubble propagation, on the other hand, the restoring forces that affect bubble propagation are absent. A formula which relates the coercive force measured by the two techniques is derived. The theory is tested with experimental data on 1.8-μm and 3-μm films of the composition {Y,Sm,Lu,Ca}3[Fe,Ge,Lu]2 (Fe,Ge)3O12.

Coercive Properties of Magnetic Garnet Films

“…Slonczewski [102] and Thiele [103] showed that dynamic coercivity should be added to the applied field component parallel to the bubble velocity. Walling [104] suggested a model explain the difference between the static coercivity of bubble domains (H c hyst ) and the coercivities measured dynamically (H c prop ). He measured the start field of the motion of stripe domains (which he took for H c hyst ) and the start field of a single bubble domain motion (H cs in Patterson's term) together with the v = 0 extrapolated term, measured by ac wall oscillation.…”

“…[104] suggested a model expl the difference between the static coercivity of bubble domains (Hc hyst ) and the coercivit measured dynamically (Hc prop ). He measured the start field of the motion of stripe doma (which he took for Hc hyst ) and the start field of a single bubble domain motion (Hcs in P terson's term) together with the v = 0 extrapolated term, measured by ac wall oscillati In this calculation, the wall structure of domains was not taken into consideration.…”