Three-Dimensional Stress and Magnetic Anisotropy Analyses for Thin Film Heads

Stresses were calculated using the three-dimensional finite element method. There are two kinds of stresses, thermal and intrinsic. The latter were treated as equivalent thermal stresses and represented using modified thermal expansion coefficients. Modified values for films were selected so as to fit the calculated displacements to measured results, for circular substrates with a deposited layer. The accuracy of calculations was within 20% of measurements, and stress distributions near backgaps qualitatively corresponded to the domain structure observed by spin-polarized SEM. It was found that tensile stresses along the hard axis are dominant in the pole tip region. The dependence of the magnetic anisotropy on the magnetostriction constant was calculated using the stresses thus obtained. Suitable magnetostriction constants for the bottom yoke were found to be smaller than those for the top yoke.