| Abstract: | Co/Ti multilayers with wedge-shaped Co or Ti sublayers were prepared using UHV (5×10−10 mbar) DC/RF magnetron sputtering. The planar growth of the Co and Ti layers was confirmed in situ by X-ray photoelectron spectroscopy. Cobalt sublayers grow on sufficiently thick titanium sublayers in the soft magnetic nanocrystalline phase up to a critical thickness dcrit3.0 nm. For a thickness greater than dcrit, the Co sublayers undergo a structural transition to the polycrystalline phase with much higher coercivity. Furthermore, for the Co/Ti multilayers with nanocrystalline Co sublayers with dCo=2.7 nm we have observed a significant drop of the coercivity — typically from Hc3.5 kA/m to Hc0.2 kA/m — for Ti thickness dTi0.35 nm. The above effect could be explained by the existence of a minimum Ti sublayer thickness (dmin0.35 nm), which is required for the nanocrystalline growth of Co, and/or the formation of quasi-continuous non-magnetic layers for dTidmin giving rise to a decrease of the exchange energy between Co sublayers. Magnetic domains and walls studies revealed the structural transitions of the Co sublayers. |
