Composite magnetic films for optically assisted magnetic recording (rapid thermally annealed FePt crystalline grains/magneto optical recording film)

在本研究中，我们讨论了由下层FePt晶粒和连续层TbFeCo组成的复合磁记录介质作为超过1 Tbit/ In ^2的高密度光辅助记录介质。FePt具有较高的磁各向异性K_u和形成小晶粒的能力，是克服小磁性晶粒热波动的高密度磁记录介质的首选。快速热退火法制备FePtX （X=Cu, Ni）。为了提高FePtX晶粒的面堆积密度，采用具有自组织纳米孔的SiO_2衬底作为纳米模板。主要研究结果如下：1)自组装法制备纳米凹痕阵列衬底。我们成功地制备了内部具有高度有序纳米孔的SiO_2薄膜，并发现用乙醇稀释溶剂可以有效地稀释自旋取芯法制备的薄膜厚度。2) Cu或Ni的掺入降低了FePt的居里温度，以Cu或Ni代替部分Fe有望降低K_u即居里温度T_c （FePt，室温T_c=500℃）。通过RTA法制备了隔离良好的FePtX（X=Cu, Ni）粒子，并证实了掺杂对降低居里温度的作用。各元素之间存在不同的含量依赖性。3)复合磁记录介质中畴形的微磁模拟结果表明，由层下FePt晶粒和TbFeCo连续层组成的复合磁膜可以形成微小的畴（TbFeCo表面的畴直径为22 nm）。即使各晶粒间距的减小小于理论畴壁宽度，FePt粒子仍作为TbFeCo层的畴钉位点。

In this study, we discussed the composite magnetic recording media, consisting of FePt grain under layer with TbFeCo continuous layer, as high density optically assisted recording media over 1 Tbit/in^2. Due to its high magnetic anisotropy K_u and the capability of forming small grains, FePt is a leading candidate for high density magnetic recording media that are preferable to overcome the thermal fluctuation of small magnetic grains. FePtX (X=Cu, Ni) prepared by Rapid Thermal Annealing (RTA). To increase areal packing density of FePtX grains, a SiO_2 Substrate having self-organized nano-pores was used as a nano-template. Main results were followings1) Fabrication of nano-dent array substrate by self-assemble methodWe succeeded to fabricate SiO_2 film having highly ordered nano-pores inside, and found that the dilution of a solvent with ethanol is effective to thinning the film thickness preparing by spin coring method.2) Decrease of the Curie temperature of FePt by Cu or Ni dopingSubstituting Cu or Ni for some of the Fe is expected to reduce the K_u i. e. Curie temperature T_c (FePt, T_c=500℃ at room temperature). We fabricated well isolated FePtX(X=Cu, Ni) particles by RTA, and confirmed the doping effect to reducing Curie temperature. Deferent content dependence was found in each element.3) Micro-magnetic simulations of domain shape incomposite magnetic recording mediaSimulated result of composite magnetic film consisting of FePt grains under layer and TbFeCo continuous layer shows tiny domain could be formed (domain diameter 22 nm at the TbFeCo surface). Even the spacing between each grain decreased less than the theoretical domain wall width, FePt particles act as domain pinning sites of TbFeCo layer.