  In this work we examine synthetic antiferromagnetic structures consisting of
two, three, and four antiferromagnetic coupled layers, i.e., bilayers,
trilayers, and tetralayers. We vary the thickness of the ferromagnetic layers
across all structures and, using a macrospin formalism, find that the nearest
neighbor exchange interaction between layers is consistent across all
structures for a given thickness. Our model and experimental results
demonstrate significant differences in how the magnetostatic equilibrium states
of even and odd-layered structures evolve as a function of the external field.
Even layered structures continuously evolve from a collinear antiferromagnetic
state to a spin canted non-collinear magnetic configuration that is
mirror-symmetric about the external field. In contrast, odd-layered structures
begin with a ferrimagnetic ground state; at a critical field, the ferrimagnetic
ground state evolves into a non-collinear state with broken symmetry.
Specifically, the magnetic moments found in the odd-layered samples possess
stable static equilibrium states that are no longer mirror-symmetric about the
external field after a critical field is reached. Our results reveal the rich
behavior of synthetic antiferromagnets.
