Oscillations of the Curie temperature and interlayer exchange coupling in magnetic trilayers

The onset of long-range magnetic order in exchange-coupled epitaxial Co/Cu/Ni trilayers, 2–4 monolayers (ML) each, on Cu(001) is studied by element-specific x-ray magnetic circular dichroism between 30 and 300 K in ultrahigh vacuum. Oscillations of the enhancement of the ordering temperature of Ni $\left(\Delta T_{\mathrm{Ni}}\right)$ by more than 40 K are measured as a function of interlayer exchange interaction by varying the Cu(001) spacer thickness. Below a Cu thickness of 2.3 ML antiferromagnetic coupling is measured. The period, phase, and amplitude of the $\Delta T_{\mathrm{Ni}}$ oscillations are in excellent agreement with the theoretical prediction for the short- and long-period oscillations of the interlayer exchange coupling.