Rahman M Tofizur, Shams Nazmun N, Lai Chih-Huang
Department of Materials Science and Engineering, National Tsing Hua University, Hisinch-30013, Taiwan.
Nanotechnology. 2008 Aug 13;19(32):325302. doi: 10.1088/0957-4484/19/32/325302. Epub 2008 Jul 2.
Large-area, over several square centimeters, mesoporous array of magnetic nanostructure with perpendicular anisotropy is prepared by depositing Co/Pt multilayers (MLs) on a mesopore array of anodized alumina (AAO) fabricated on Si wafers. The MLs are mainly deposited on the top of AAO walls and perimeters of the pores; very small amounts of magnetic material reach the bottom due to the high aspect ratio of AAO. Consequently, ordered pores are present in the magnetic MLs. The mean pore diameter of the fabricated mesoporous array is 8.83 nm with a standard deviation of 3.16 nm and density of about 2.1 × 10(11) cm(-2). The Co/Pt MLs deposited on AAO and Si both exhibit strong perpendicular magnetic anisotropy, but the perpendicular coercivity (H(c)) increases by 15 times on AAO compared to that on Si. On the other hand, the magnetic cluster size decreases from 1000 nm (on Si) to 100 nm due to the presence of high-density pores. The dramatic increase in H(c) and the decrease in magnetic cluster size suggest that the pores behave as effective pinning sites. The magnetization-switching characteristics of the fabricated porous structure are different from those of the continuous films or Stoner-Wohlfarth-type (S-W) particles. One of the potential applications of this mesoporous structure may be in the field of high-density magnetic data storage.
通过在硅片上制备的阳极氧化铝（AAO）介孔阵列上沉积Co/Pt多层膜（MLs），制备出具有垂直各向异性的大面积（超过几平方厘米）磁性纳米结构介孔阵列。MLs主要沉积在AAO孔壁顶部和孔周边；由于AAO的高纵横比只有极少量磁性材料到达底部。因此，在磁性MLs中存在有序的孔。制备的介孔阵列平均孔径为8.83nm，标准偏差为3.16nm，密度约为2.1×10(11)cm(-2)。沉积在AAO和硅上的Co/Pt MLs均表现出很强的垂直磁各向异性，但与在硅上相比，在AAO上垂直矫顽力（H(c)）增加了15倍。另一方面由于高密度孔的存在，磁簇尺寸从1000nm（在硅上）减小到100nm。H(c)的显著增加和磁簇尺寸的减小表明这些孔起到了有效的钉扎位点作用。制备的多孔结构的磁化翻转特性不同于连续薄膜或斯托纳-沃尔法斯（S-W）型颗粒。这种介孔结构的潜在应用之一可能在高密度磁数据存储领域。
