纳米晶软磁薄膜Fe-Ti-N的结构、磁学性能和热稳定性研究

THE STRUCTURE, PROPERTIES AND THERMAL STA- BILITY OF THE NANOCRYSTALLINE Fe-Ti-N SOFT MAGNETIC FILMS

在高溅射功率900 W 下用RF磁控溅射方法制备了厚为630-780nm的Fe-Ti-N薄膜,结果表明:当膜成分(原了分数, ％.下同)在Fe-3.9Ti-8.8N和Fe-3.3Ti-13.5N范围内,薄膜由α’和Ti2N沉淀组成,磁化强度4πMs超过纯铁,最商可达2.38T:而矫顽力Hc下降为89 A/m.可以满足针对1.55 Gb/cm2高存储密度的GMR/感应式复合读写磁头中写入磁头的需要.N原子进入α-Fe使α’具有高饱和磁化强度;Ti的加入,阻止α’→α’+γ’的分解,稳定了强铁磁性相α’.是Fe-Ti-N具有高饱和磁化强度的原因.由于由晶粒度引起的对Hc的影响程度HcD与晶粒度D有以下关系:HcD∝D6,晶粒度控制非常重要.N原了进入α+Fe点阵的八面体间隙,引起极大的畸变,使晶粒碎化.提高溅射功率也使晶粒度下降.两者共同作用,能使晶粒度下降到约14nm,使Hc下降,晶界是择优沉淀地点,在α’晶界上沉淀Ti2N能起钉扎作用,阻止晶界迁移,使纳米晶α’不能长大。

Fe-Ti-N magnetic films were deposited with high sputtering power of 900 W. When the composition (atomic fraction, %) of the film is in the range between Fe-39Ti-8.8N and Fe-3.3Ti-13.5N, the film is composed of alpha' and Ti2N precipitates, the 4piM(s), is higher than that of pure iron, reaches a maximum of 2.38 T and the H-c is reduced to a minimum of 89 A/m. The film could meet the needs of the recording head in the dual-element GMR/inductive heads for 1.55 Gb/cm(2) high storage density. The incorporation of N in alpha-Fe brings about the high saturation magnetization of the alpha'phase. The Ti addition inhibites the equilibrium decomposition of alpha' --> alpha+gamma' and stabilizes the strong ferromagnetic phase alpha'. Because H-c(D) proportional to D-6, the grain size control is very important. The nitrogen induces severe distortion of the a' lattice, which could break the grain to pieces and reduce the grain size. High sputtering power also leads to the formation of fine grain of about 14 mn. Ti2N preferentially precipitated at the grain boundary could pin the grain boundary and prevent the grain growth. The stable temperature of the structure and coercivity is not less than 520 degreesC.