Magnetic properties of Co/Al2O3/Co junctions deposited by ultra high vacuum ion beam sputtering

Cobalt and alumina layers are deposited by UHV ion beam sputtering to elaborate Co/Al2O3/Co junctions. To form the Al2O3 insulator barrier, oxygen is introduced into the chamber during the aluminum target sputtering. The experimental conditions to obtain stoichiometric Al2O3 are determined using auger electron spectrometer (AES) and Rutherford backscattering spectroscopy (RBS). Stoichiometric Al2O3 is obtained with an oxygen pressure of 6×10−7 mbar, i.e. a deposition rate of 0.5 Å/mn, and a beam intensity of 55 μA. Magnetic properties of the Co bottom electrode and the mutilayers are studied by magneto-optical Kerr effect (MOKE) and by alternating gradient field magnetometry (AGFM). The easy axis of magnetization is in-plane and the Co layers present an in-plane anisotropy. Moreover, the Co bottom electrode is paramagnetic for a thickness below 40 Å, at room temperature.