Influence of Anisotropy Dispersion on Magnetic Properties of Ni–Fe Films

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Abstract
The dispersion of the magnetic anisotropy was monotonically increased in several Ni–Fe films by subjecting them to increasingly severe heat treatments, and the room‐temperature magnetic properties were monitored after each anneal by Lorentz electron microscopy. A gradual transition towards increasingly anomalous properties in a single film was thereby observed. An increase, with annealing, of the magnetization ripple intensity, the measured angular anisotropy dispersion, and the wall coercive force Hw was found. After sufficient annealing, locking was seen upon reversal parallel to the easy axis; further annealing increased the locking‐wall density. The anisotropy field Hk monotonically decreased with annealing until the uniaxial character of the film was lost and it became a rotatable‐initial‐susceptibility (RIS) film. Reversal at azimuths away from the easy axis proceeded by labyrinth propagation after the early anneals, but by partial rotation after more severe annealing.