Dominant role of thermal magnon excitation in temperature dependence of interlayer exchange coupling: Experimental verification

Ultrathin Ni∕Cu∕Co trilayers were deposited in ultrahigh vacuum and the ferromagnetic resonance measured in situ as a function of both, temperature and out-of-plane angle of the external field. The interlayer exchange coupling Jᵢₙₜₑᵣ was then unambiguously extracted at various temperatures, entirely from the angular dependence of the resonance field positions. The temperature dependence of Jᵢₙₜₑᵣ(T) follows an effective power law ATⁿ,n≈1.5. Analysis of the scaling parameter A shows an oscillatory behavior with spacer thickness, as does the strength of the coupling at $T=0$. The results clearly indicate that the dominant contribution to Jᵢₙₜₑᵣ(T) is due to the excitation of thermal spin waves and follows recently developed theory closely.