Strong temperature dependence of the interlayer exchange coupling strength in Co/Cu/Co sandwiches

We present a study of the temperature dependence of the interlayer coupling strength in Co(hcp)/Cu sandwiches. The thermal variation of the coupling has been studied between 20 and 300 K by superconducting quantum interference device magnetometry for the samples corresponding to the first and second maxima in the oscillation of the exchange coupling of a series of $\mathrm{C}\mathrm{o}/\mathrm{C}\mathrm{u}{(t}_{\mathrm{Cu}})/\mathrm{C}\mathrm{o}$ trilayers. We find a very strong decrease of the exchange coupling strength between 20 and 300 K. We show that the existing theoretical models cannot explain this unusual strong decrease. However, we believe that this behavior could be due to the confinement of carriers of one spin orientation in the spacer layer.