Slow motion of magnetic domain walls in grainhyphen;oriented 50hyphen;50percnt; NiFe is studied experimentally and theoretically. There is a region in which velocityuis approximately exponentially dependent on fieldH. It is found that all of the data may be fit by a theoretical expression derived from the spring model, and the assumption of quantumhyphen;mechanical tunneling as the mechanism responsible for slow motion. However, the values of the parameters derived from the best fit lead to a value of the separation, at breakaway, between the midpoints of an average pinning center and that portion of a wall pinned by it which is about 4times;10minus;13lattice constants, which is unrealistically small. It is tentatively concluded that tunneling is not the mechanism behind slow wall motion, at least not at room temperature.
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