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A three-dimensional micromagnetic model has been developed to study single pole write heads with soft magnetic underlayer ͑SUL͒ for perpendicular recording at extremely small track widths. The study points out that at any practical ABS-to-SUL spacing, the maximum head field within the recording media at deep submicron track width and pole-tip thickness becomes significantly smaller than the ideal value of 4M s . Head field gradient in the medium also degrades with decreasing track width. Maintaining the conventional design, a significantly large remanent head field develops for track width below 100 nm, presenting danger of erasing previously recorded bits. The origin of the large remanent head field is the failure for a pole tip to reach a completely demagnetized state due to the overwhelming ferromagnetic exchange energy at the deep submicron pole-tip dimensions.

The effect of stress in soft magnetic thin films, in particular, on the in-plane anisotropy, has been studied, based on the analysis of the magnetoelastic energy associated with the stress. The easy-axis directions and the effective anisotropy constants have been identified, as functions of the stress, the magnetostriction coefficients of the material, and the growth texture of the film. The magnetoelastic energy has been combined into an existing micromagnetic model to simulate the magnetization of thin films with various materials, stress states, and growth textures. Simulation results of static magnetic domain structures are in agreement with the theoretical predictions.

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Magnetization dynamics during field reversal in thin film recording heads are studied via micromagnetic modeling. It is found that head field reversal under the current field can be characterized by two stages: an initial stage that is mainly governed by the gyromagnetic motion and virtually independent of energy damping, followed by a damping stage that strongly depends on the energy damping constant. Due to the finite energy damping in practical recording heads, the head field amplitude will roll off at high recording frequencies. Simply decreasing the current rise time or increasing current amplitude will not alleviate the situation, but rather worsen it. There exists an optimum current rise time at which the head field rise time is minimized and the roll-off frequency is maximized.

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