Correlation between structural and magnetic properties in wedged Ti/Co multilayers

The Ti/Co multilayers (MLs) with wedge shaped Ti and constant-thickness Co (d(Co) = 2 nm) sublayers were prepared using an UHV DC/RF magnetron sputtering. Results showed that the average grain size of the Co sublayer strongly depends on the Ti thickness. The Ti/Co MLs with d(Ti) < 0.1 nm grow in the polycrystalline phase. For d(Ti) approximate to 0.2 nm the in-plane Co grains size rapidly decreases. We have estimated an average grain size of the Co sublayer as small as D approximate to 4 nm. For thicker Ti sublayer D first increases and then decreases, reaching a maximum D approximate to 14 nm for d(Ti) approximate to 0.28 nm. Coercivity measurements showed that for d(Ti) approximate to 0.2 nm and d(Ti) > 0.37 nm the Co sublayers grow in the soft magnetic nanocrystalline phase with the average grain size well below the magnetic exchange length (L-ex approximate to 10 nm).