title: Naturally Produced Co/CoO Nanocrystalline Magnetic Multilayers: Structure and Inverted Hysteresis.
abstract: Cobalt-based multilayers with excellent sequencing are grown via radiofrequency magnetron sputtering with the use of one Co target and natural oxidation. The Co layers are continuous, fully textured {111} and have the face centered cubic structure. At the end of deposition of each Co layer air is let to flow into the vacuum chamber via a fine (leak) valve. The top of Co is oxidized. The oxidized layers consist of cubic CoO crystallites. Near the film surface hexagonal Co(OH)2 is also detected. Magneto-optical Kerr effect hysteresis loops show in-plane magnetized films. The magnetic saturation field in the out-of-plane measurements is large exceeding 12 kOe. This observation supports indirectly the fact that Co is face centered cubic; if it was c-axis textured hexagonal the magnetocrystalline anisotropy would be large resulting in smaller values of the saturation field. As the Co-layer thickness decreases the in-plane loops show reduced remanence, slow approach to magnetic saturation and the out-of-plane loops show inverted hysteresis and/or crossing loop features with sizeable remanence. The effects are discussed with respect to the enhanced orbital magnetic moment of Co and the antiferromagnetic coupling between Co spins at the Co/CoO interface.
authors.forename: Francesca
authors.initials: F
authors.lastname: Santarossa
authors.forename: Spiridon D
authors.initials: SD
authors.lastname: Pappas
authors.forename: Andreas
authors.initials: A
authors.lastname: Delimitis
authors.forename: Andreas
authors.initials: A
authors.lastname: Sousanis
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Poulopoulos