The effect of stress-induced anisotropy in patterned FeCo thin-film structures

In this work, 1-mu m-thick FeCo films with -320 MPa compressive stress and FeCo/NiFe films with 600 MPa tensile stress were patterned into 5x20 mu m(2) elements. The stress anisotropy resulting from patterning was measured using x-ray diffraction to be 220 MPa for the tensile films and -170 MPa 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 50 MPa should result in an easy axis rotation, and are in agreement with the experimental results. (C) 2006 American Institute of Physics.