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Two-dimensional domain-wall configurations and dynamics in thin films with the easy axis parallel to the film plane are calculated by using LaBonte-like energy minimization as well as solving the Landau-Lifshitz equation with phenomenological damping. Under a sufficiently small uniform field applied in the easy direction, the effective wall mass and the viscosity coefficient induced from a uniform wall motion are compared with theoretical values. For external fields much greater than the anisotropy field, the wall motion exhibits complex features, including periodic transitions between asymmetric Bloch and Neel wall structures and the emergence of multivortices, depending on the film thickness. The latter serves as a precursor to turbulent wall dynamics at even higher external fields. With a varying external field applied in the hard direction and parallel to the film surface, wall structure changes between asymmetric Blochand Neel-type walls are also seen. An irreversible transition is observed which causes a constricted hard-axis hysteresis loop. Dynamically, this hysteretic transition can be associated with wall creep.

An increase in external temperature or internal heating by writing can induce protrusion or strain of thin film layers in a magnetic recording head. To profile the protrusion, the surface topography and the temperature distribution are imaged in fixed heads by scanning probe and optical microscopy. Near the poles and the shields, the protrusion is at a peak, producing a risk of head-disk interaction. The dynamics are elucidated in flying heads over a disk by measuring the amplitude of a reference pattern with the read head. The temporal profiling technique can be applied both in component testing on spinstands and reliability testing in fully integrated disk drives. For either heating or cooling of the heads, the characteristic time constant for protrusion is 100 s and reaches 95% of the plateau after 1 ms. The protrusion is linear with temperature and is reversible, implying that the strains are within the elastic limit. Furthermore, variation of the write pulse shape suggests that Joule heating is more significant than eddy current or hysteresis losses in inducing protrusion.Index Terms-Magnetic heads, magnetic recording mechanical factors, strain, thermal protrusion.

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