Monitoring Net Anisotropy Fields of Recording Heads by Ferromagnetic Resonance

Monitoring Net Anisotropy Fields of Recording Heads by Ferromagnetic
Resonance

      Ferromagnetic resonance (FMR) is used to determine the net
effective anisotropy field, Hk, of a magnetic recording head.  Using
a commercial FMR spectrometer the resonance fields of the head are
measured as a function of the angle of the applied field.  The
resonance fields are analyzed in terms of the Landau-Lifshitz
equation to provide effective anisotropy fields.  By subtracting the
demagnetizing field knwon from the geometry of the head, the
contributions to the effective anisotropy field related to film
composition and stress can be obtained.  The net anisotropy fields
are detected for the central yoke region of the permalloy film.  FMR
is sensitive to all permalloy layers (P1, P1S, P2, P2S), so no
assignment of responsible film/films is made.  By using test
structures which do no require process changes, the anisotropy in
single films (ex.  P1 or P2) can be monitored individually.