Short period magnetic coupling oscillations in Co∕Si multilayers: Role of crystallization and interface quality

In this work we show, in a transition-metal-semiconductor system, that both the interfacial quality and the crystallographic structure of the samples play an important role to allow the observation of the predicted properties of the system. To reduce the interfacial mixing, Co∕Si multilayers were grown at 90 K and different crystallization qualities have been obtained by depositing the samples on glass and silicon substrates. To be able to observe experimentally the short period magnetic coupling oscillations predicted by theoretical computations, the Si spacer layers must be in a crystalline form and the interfacial mixing to be reduced to 5 atomic planes. However, the role of the crystallographic structure or growth direction of the Si layer seems to be weak. This is in agreement with the theoretical computations suggesting that the magnetic properties of such a system are driven by the presence of quantum well states at the Fermi level of the semiconductor regardless of its crystallographic structure.