In this work, 1-μm-thick FeCo films with −320MPa compressive stress and FeCo∕NiFe films with 600MPa tensile stress were patterned into 5×20μm2 elements. The stress anisotropy resulting from patterning was measured using x-ray diffraction to be 220MPa for the tensile films and −170MPa for the compressive films and is in agreement with finite element modeling. Scanning electron microscopy with spin-polarization analysis imaging shows that the domain structure of the elements was influenced by this stress-induced anisotropy. Calculations of the effect of stress anisotropy were performed on domain configurations for the patterned structures. Results indicate that tensile stresses should reinforce closure domains, while compressive stresses of magnitude greater than 50MPa should result in an easy axis rotation, and are in agreement with the experimental results.
Stripe domains caused by perpendicular anisotropy degrade soft magnetic properties of thin films used in recording heads. In this work, the relationship between stress and the susceptibility to stripe domains in soft magnetic thin films is studied theoretically and experimentally. The critical stripe domain onset thickness of a polycrystalline film with cubic unit cell under a planar, isotropic stress is calculated as a function stress and texture for sputtered FeAlN and CoFe films. In good agreement with experimental data, the results show that the stripe domain onset thickness depends on stress and texture. In the sputtered Co65Fe35 film, a residual stress close to zero helps eliminate the possibility of stripe domains, while in the sputtered FeAlN film, the role played by stress depends on texture. For the most frequently seen (110)-textured FeAlN film, large compressive stresses help reduce the possibility of stripe domains for low and moderate N concentrations.
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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