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We report a systematic study on the anisotropy symmetry, magnetic domains and magnetic relaxation behavior in Co thin films deposited on MgO (001) substrate by varying (i) the pre-annealing condition and (ii) the speed of substrate rotation during deposition. Substrate annealing prior to deposition leads to the formation of textured thin films. On contrary Co films prepared without substrate pre-annealing exhibit polycrystalline nature. Surface topography imaged by atomic force microscopy (AFM) depicts a profound effect of growth condition on grain size and its distribution. Magnetic hysteresis measurement along with simultaneous domain imaging has been performed by magneto optic Kerr effect (MOKE) based microscope by varying the angle (ϕ) between the easy axis and the direction of applied magnetic field. We observed the existence of cubic and uniaxial anisotropy due to the presence of substrate annealing and oblique angular deposition, respectively. Along the easy axis, magnetization reversal is governed by 180° domain wall motion via branched domains. However, for easy axis

Magnetic Antidot Lattice (MAL) arrays of Co have been prepared in micron range using ultraviolet (UV) lithography technique with different shapes and sizes. Magnetization reversal in such MAL systems has been studied by magneto-optic Kerr effect (MOKE) based microscopy by varying the angle between the easy axis and the external magnetic field. The domain images evidence that the magnetization reversal along easy axis is highly dominated by nucleation of domains which is subsequently accompanied by domain wall motion. We have observed that with increase in active magnetic area domain size increases but on the contrary coercivity decreases. The presence of periodic holes turns the MALs magnetically hard when compared to similar thickness of continuous thin film. The magnetization relaxation along easy axis for the Co MAL at constant dc field fits very well with the exponential law of Fatuzzo–Labrune indicating domain nucleated dominant process.

In this paper, we study the domain wall dynamics in high magnetic flux density (–1.85 T) of soft magnetic ribbons Fe81.2Co4Si0.5B9.5P4Cu0.8 prepared with various annealing conditions. It is observed that annealing these ribbons beyond a temperature (C) crystalizes the alloy with the appearance of α-Fe(-Co) phase. The post annealing leads to a change from amorphous to nanocrystalline phase accompanied by a reduction in internal stress in the ribbons. Domain imaging has been performed under both dc and ac fields to study the domain wall behavior in these ribbons. A wide variety of domain structures are observed in ribbons prepared with different annealing temperature as a result of the change in the intrinsic anisotropy. Under an ac magnetic field, the 'stress patterns' in the amorphous ribbons are robust. However, ribbons with reduced stress (i.e. nanocrystalline) exhibit domain wall propagation which hints at a significant reduction in magnetocrystalline and magnetoelastic anisotropies due to uniform nanocrystallization. The ribbon annealed at C exhibits static domain patterns resulting from strong pinning centers created by Fe-B precipitates.

Epitaxial FePt thin films with various thicknesses, having in-plane uniaxial magnetic anisotropy, have been prepared at different deposition temperatures using sputtering technique. L10 ordering in the FePt thin film leads to very large uniaxial magnetocrystalline anisotropy. The magnetocrystalline anisotropy energy increases with the increase in film thickness and deposition temperature. Domain imaging performed by Magneto-optic Kerr microscopy with a longitudinal geometry suggests that the domain structure and magnetization reversal process strongly depend on the film thickness and the deposition temperature. For the films deposited at a certain temperature, there exists a critical thickness where the coercive and saturation fields show maxima.