Inverse magnetostriction effect on magnetoresistive response for evaporated NiFe and NiFeCo films

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Abstract
The relations between inverse magnetostriction energy ε and magnetoresistive (MR) response have been investigated for Ni82Fe18 films and Ni82Fe12Co6 films that have about twice the uniaxial anisotropy energy as the NiFe films. To obtain films with various ε values (50–800 J/m3), internal stress σ for the films is changed by the deposition conditions and film thickness control. The σ is measured by the bending method. The σ changes for both films are related to microstructure differences. Hysteresis or Barkhausen jump is observed for the NiFe films with absolute ε value ‖ε‖ more than 120–130 J/m3, and for the NiFeCo films with ‖ε‖ more than 300–330 J/m3. The threshold ‖ε‖ values are on the same order of magnitude as the calculated uniaxial anisotropy for each film. To obtain smooth MR response, it is very important to reduce the ‖ε‖ to less than the uniaxial anisotropy energy value, by deposition conditions and film thickness control.