Preferential alignment of Co moments at oxide/Co interface in Si/Co/Co-oxide/Cowedge/Pt structure

• Published in: Thin solid films Vol. 709; p. 138246
• Main Authors: Jamal, Md. Shahid, Gupta, Pooja, Kumar, Dileep
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2020
• Subjects: Anisotropic magnetoresistance; Electron-beam evaporation; Interface; Magnetic thin films; Perpendicular magnetic anisotropy; Anisotropic magnetoresistance; Perpendicular magnetic anisotropy; Electron-beam evaporation; Magnetic thin films; Interface
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2020.138246

•Preferential alignment of the Co spins at CoO/Co bilayer due to interface oxidation.•Wedge shaped sample of length 55 mm for thickness dependent studies.•Information on Co spins at the interface using transverse and longitudinal magnetoresistance.•Co–O bonds alignments at interface due to Co–O hybridization.•C-axis alignment preferentially perpendicular to the film surface due to bond alignment. Magnetization reversal process in Si/Co/Co-oxide/CoWedge/Pt structure with increasing thickness of CoWedge layer has been studied with an aim to explore the effect of interface oxidation on the preferential alignment of Co spins at Co-oxide/CoWedge interface. Oxide layer is prepared at the surface of Co layer by heating it in the presence of oxygen partial pressure. Top Co layer (CoWedge) was deposited in the form of wedge with thickness gradient ~0.11 nm/mm across the full length (55 mm) of the Si substrate. Azimuthal angle dependent magneto-optic Kerr effect and magnetoresistance measurements in both transverse and longitudinal geometries revealed that despite of degraded growth, oxidized interface is responsible for the preferential alignment of Co spins at the interface. During the initial stages of Co deposition on Co-Oxide layer, the possible Co–O hybridization at the interface leads to the Co–O bonds alignments perpendicular to the interface which helped Co layer to grow in hcp phase with c-axis aligned preferentially perpendicular to the film surface. Combined effect of volume and interface magnetic anisotropy is attributed to overcome the shape anisotropy and responsible for the origin of perpendicular magnetic anisotropy (PMA) in the CoWedge layer. Variation in PMA with increasing thickness of CoWedge (0.6 nm to 5.6 nm) could be understood primarily in terms of film morphology, which changed significantly with film thickness.