“…The twocomponent spinors Ψ † , Ψ are the creation/annihilation operators for the itinerant carriers. After integrating out the itinerant carriers 23,24,29,30 , the exchange coupling be-tween the ferromagnetic layers is described by an effective Heisenberg Hamiltonian, H eff = ij J ij S i L S j R . Within the linear response theory 31,32 , the mediated exchange coupling J ij is proportional to the static spin susceptibility tensor, 23,24,29,30…”