Magnetic trilayers with bilinear and biquadratic exchange
couplings: Criteria for the measurement of J1 and J2

      C. Chesman, M. A. Lucena, M. C. de Moura, A. Azevedo, F. M. de
Aguiar, and S. M. Rezende 
      Departamento de Física, Universidade Federal de Pernambuco,
50670-901 Recife, Brazil 

      S. S. P. Parkin 
      IBM Research Division, Almaden Research Center, 650 Harry Road, San
Jose, California 95120-6099 

(Received 9 February 1998) 

We have analytically calculated phase boundaries of magnetic trilayers
with bilinear and biquadradic exchange couplings in order to investigate
possible phase transitions in these systems as the
external magnetic field, applied either along an easy or a hard
magnetization axis, is varied. A simple scheme is obtained for both
antiferromagnetic and ferromagnetic couplings that is shown to be
consistent with magnetization curves previously measured in different
systems. In addition, experimental data regarding static and dynamic
responses in sputtered (100) Fe(40Å)/Cr(tCr)/Fe(40 Å) are
reported for the Cr thickness in the range 15 Å < tCr < 35 Å. As a result,
our model calculations indicate that the bilinear and biquadratic exchange
coupling constants, J1 and J2, cannot be accurately
determined from a fit to the experimental data when the ratio J2/|J1| > 1,
and if only the main magnetization axes are considered. ©1998 The American
Physical Society 

URL: http://publish.aps.org/abstract/PRB/v58/p101