New antiferromagnetic insulator superlattices: Structural and magnetic characterization of (${\mathrm{FeF}}_2$${)}_{\mathit{m}}$(${\mathrm{CoF}}_2$${)}_{\mathit{n}}$

High-quality antiferromagnetic (AF) superlattices (${\mathrm{FeF}}_2$ ${)}_{\mathit{m}}$(${\mathrm{CoF}}_2$ ${)}_{\mathit{n}}$, as judged from high-resolution x-ray diffraction (HRXD), were grown on (001) ${\mathrm{ZnF}}_2$ substrates. Using HRXD, the thermal-expansion coefficient ${\mathrm{\alpha }}_{\left[001\right]}$(T) vs T was measured. While two shifted AF anomalies are seen for (m,n)=(25,30), only one is observed for (m,n)=(19,6). Comparison of ${\mathrm{\alpha }}_{\left[001\right]}$(T) in the two superlattices with that of ${\mathrm{FeF}}_2$ and ${\mathrm{CoF}}_2$ indicates that a significant redistribution of the magnetic entropy occurs.