耐高温垂直取向FePt 连续薄膜的表面形貌与磁性

用磁控溅射法在加热到400℃的MgO(001)单晶基片上沉积了总厚度为25 nm 的Fe(0.6 nm)/Fe_30.5Pt_69.5(1.9 nm)]₁₀ 多层连续薄膜, 总成分配比为Fe₅₀Pt₅₀. 然后对其在500, 900]℃温度范围进行真空热处理, 分析了热处理温度对薄膜表面形貌、晶体结构以及磁特性的影响. 结果表明, 在加热基片上生长的FePt 薄膜, 层间已经发生扩散, 形成无序的A1 相. 经过700℃以上的高温热处理, 薄膜转变为具有(001)织构的L1₀相FePt 合金, 易磁化轴沿垂直于膜面的方向, 有序度大于0.85, 单轴磁晶各向异性能约2.7×10⁷ erg/cc. 利用扩散后残存的周期性微弱成分起伏, 可以使薄膜在800℃以下保持形貌连续. 用原子力显微镜对薄膜表面进行观察证实, 在780℃进行热处理, 薄膜的表面最平整. 这种优质的连续薄膜可以应用于微加工制作超高密度垂直磁记录阵列介质.

Morphology and magnetic properties of vertically orientated continuous FePt films annealed at high temperature

By magnetron sputtering, Fe(0.6 nm)/Fe_30.5Pt_69.5(1.9 nm)]₁₀ continuous multilayer films with nominal composition of Fe₅₀Pt₅₀ and total thickness of 25 nm were deposited on MgO(001) substrates heated to 400°C, and then subjected to a vacuum annealing at temperatures in the range of T_a = 500, 900]°C. The morphology, crystallography as well as magnetic property dependences of T_a were investigated by scanning electron microscope, atomic force microscope, X-ray diffraction and vibrating sample magnetometer. Heating the substrate during sputtering resulted in interlayer diffusion, and the as-deposited multilayer film showed the soft magnetic behaviors of FePt alloy with disordered A1 phase. Annealed at T_a≥700°C, the film became the ordered L1₀ phase with significant (001) orientation; the ordering parameter was more than 0.85; the magnetocrystalline anisotropic energy exceeded 2.7×10⁷ erg/cc. Due to the residual subtle periodical compositional fluctuation in the film, the ordering could nucleate interior the film and the Pt-enrichment boundaries were sufficiently suppressed. The continuity of morphology was maintained at T_a≤800℃. The observation by atomic force microscope indicated that the film annealed at T_a = 780°C had the flattest surface with sparse swells lower than 3 nm. This kind of heat-resisting continuous film would fit the need for microfabrication of patterned arrays of L1₀ FePt for applications such as the perpendicular magnetic recording media.