Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The dynamic matrix method was employed to perform theoretical calculations for investigating both static and
dynamic characteristics of thick ferromagnetic films. This approach considers situations where a noncollinear
equilibrium magnetization exists along the thickness due to a thickness-dependent uniaxial anisotropy and inter-
facial interactions in a synthetic antiferromagnet. In the former scenario, the study exposes a correlation between
noncollinear static magnetization and a nonmonotonic dependence of ferromagnetic resonance frequency, where
a frequency decrease is observed at low fields in the unsaturated regime. Regarding the synthetic antiferromagnet
structure, the research demonstrates noncoherent magnetization rotation in the spin-flop regime, with twisted
magnetization states influencing the critical and nucleation fields that define the spin-flop region. The results of
the investigation were compared to the macrospin approach, where the magnetization is assumed to be uniform
along the thickness. The study suggests that the contribution of noncollinear magnetic moments may mimic the
role of the biquadratic interaction in the macrospin model, implying that such a biquadratic term may be over-
estimated in coupled ferromagnetic films with thicknesses exceeding the material’s intrinsic exchange length.
Finally, the model was compared with experimental data obtained from a Py/Ir/Py synthetic antiferromagnet,
demonstrating that the theoretical consideration of a twisting equilibrium state of the magnetization precisely
reproduces the observed dynamic and static properties of the nanostructure.