High moment FeTiN thin films for high density recording heads

Abstract

High moment, soft FeTiN thin films were prepared by sputtering and the effects of film thickness, nitrogen concentration and annealing were investigated. It was found that a heated substrate helped to achieve a high moment and soft magnetic properties. Films thicker than 1500 /spl Aring/ deposited with no substrate heating always exhibited stripe domains, resulting in high values of the coercivity and the anisotropy field. Films deposited at elevated substrate temperatures did not have stripe domains for thickness up to 2000 /spl Aring/. Films with high nitrogen concentration exhibited /spl gamma/'-(Fe,Ti)/sub 4/N and /spl epsiv/-(Fe,Ti)/sub 3-x/N phases, resulting in low magnetization and higher coercivity. The annealing of films with low nitrogen concentration increased the magnetization, but the annealing of films with high nitrogen concentration induced a gradual phase change from the /spl gamma/'-(Fe,Ti)/sub 4/N phase to the /spl epsiv/-(Fe,Ti)/sub 3-x/N phase, resulting in lower magnetization. Our experiments confirm the stabilization of the /spl alpha/''-Fe/sub 16/N/sub 2/ phase by incorporation of Ti, but we did not achieve the 24000 Gauss magnetization reported. Films with 5 at% nitrogen showed the highest moment (20000 Gauss) and best soft (H/sub C/=3 Oe, H/sub K/=7 Oe) properties. Annealing of (Fe/sub 92/Ti/sub 8/)/sub 1-x/N/sub x/ (x=7.8 and 8.7) films deposited on glass at 130/spl deg/C indicated that the anisotropy direction is not stable when annealed at 200/spl deg/C for 2 h in a transverse magnetic field of 150 Oc.