Growth and properties of Co/Al–O x/Ni(80)Fe(20) trilayers monitored in-situ during deposition process

Abstract

The Co(25 nm)/Al( d Al)–O x /Ni 80Fe 20(25 nm), trilayers, with a Al thickness variation of 0.5 nm⩽ d Al⩽5 nm, were evaporated in ultra-high vacuum onto oxidised Si wafers. The simultaneous measurements of the magnetic hysteresis loops and thickness-dependent electric conductance were performed in-situ during deposition process. They were supplemented with surface topography and cross section images by atomic force microscopy and high-resolution transmission electron microscopy, respectively. We have shown that for an Al thickness of about 1.2 nm a transition from strongly ferromagnetically coupled Co and Ni 80Fe 20 characterised with single hysteresis loops to well separated magnetisation loops evident for weakly coupled layers occurs. The conductance measurements performed during deposition process as well as during 24 h oxidation process of the Al layer led us to the conclusion that independently on Al thickness nominally only 0.5 nm thick Al layer is oxidised. The influence of different buffer layers (Cu, Au) on magnetisation reversal characteristics is also shown.