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

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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.

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