Competition between CoOx and CoPt phases in Pt/Co/AlOx semi tunnel junctions

Houmed Garad (1) , Luc Ortega (2) , Aline Y. Ramos (3) , Yves Joly (1) , Farid Fettar (1) , Stephane Auffret (4) , Bernard Rodmacq (4) , Bernard Dieny (4) , Olivier Proux (5) , A.I. Erko

1 NEEL - SIN - Surfaces, Interfaces et Nanostructures
2 LPS - Laboratoire de Physique des Solides
3 NEEL - MRS - Matériaux, Rayonnements, Structure
4 SPINTEC - SPINtronique et TEchnologie des Composants
5 OSUG - Observatoire des Sciences de l'Univers de Grenoble

We report on the evolution of the structure and composition of a Pt(3 nm)/Co(0.6 nm)/AlOx(2 nm) trilayer sputtered on Si/SiO2 under oxidation and annealing processes by combined x-ray reflectivity and x-ray absorption studies. We describe the progressive and inhomogeneous oxidation of the layers by increasing the oxidation time. Before annealing, the layers have lower density than bulk samples and noticeable roughness. After thermal annealing, a significant improvement of the quality of the alumina layer goes along with the formation of a CoPt alloy that reduces the number of Co-O bonds. These structural outcomes clarify the evolution of the magnetic and transport properties reported at room temperature in these samples.

Mots clés: X-ray absorption; X-ray reflection; sputter deposition; platinum alloys; oxidation; platinum; nanostructured materials; nanomagnetics; nanofabrication; magnetic multilayers; cobalt alloys; cobalt; annealing; alumina

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Houmed Garad, Luc Ortega, Aline Y. Ramos, Yves Joly, Farid Fettar, et al.. Competition between CoOx and CoPt phases in Pt/Co/AlOx semi tunnel junctions. Journal of Applied Physics, 2013, 114 (5), pp.053508. ⟨10.1063/1.4816620⟩. ⟨hal-00850105⟩