Effects of Ti underlayer on the degree of order of Fe50Pt50 films

Fe50Pt50/Ti double-layer films were deposited on corning 1737F glass substrates by d.c. magnetron sputtering of FePt and Ti targets. The magnetic layer FePt was deposited at substrate temperature of 600 deg. C in order to get ordered γ1-FePt hard magnetic phase. It is found that the degree of order (S) of FePt layer increases with increasing Ti underlayer thickness. The S value for FePt single-layer film is about 0.68, and it increases to about 0.76 as the thickness of the Ti underlayer increases to 150 nm. The average grain size of the FePt film is largely reduced as the Ti underlayer is introduced. The average grain size of the single-layer FePt film is about 25 nm, it will reduced to about 12 nm as 30 nm Ti underlayer is introduced, but the average grain size of FePt is increased as the thickness of Ti underlayer is increased. Magnetic measurement indicates that the in-plane coercivity (Hcparallel) of the FePt film increases with increasing thickness of Ti underlayer, but the in-plane squareness (Sparallel) decreases