Synthesis of Carbon hcp Co fine particle encaged in Carbon nano capsules utilizing laser ablation

研究了激光烧蚀法制备的Co-C薄膜的磁性。用X射线衍射仪对Co-C薄膜的结构进行了研究。用Co-C复合靶材在玻璃衬底上沉积了Co-C薄膜(方法一)。我们还制备了不同几何形状的Co-C薄膜，即Co靶和C靶分别排列(方法2)。薄膜厚度为2 0 0Å-1 0 0Å。方法1的样品中含有钴微粒。饱和磁化强度和矫顽力分别约为1200emu/cc和300Oe。并证实得到了HCP-Co颗粒。而用X射线衍射峰估算的平均粒径为26 nm。为了将Co-C薄膜应用于磁记录介质，我们没有减小Co-C薄膜的颗粒尺寸。为了减小颗粒尺寸，我们采用了方法2，然后用退火法制备了Co-C薄膜。沉积的样品具有很小的饱和磁化强度和矫顽力。结果表明，Co颗粒非常细小。退火后，合金的饱和磁化强度和矫顽力都有所提高。但是我们没有得到HCP-Co颗粒。利用共烧蚀方法很难控制样品的结构和成分，为了严格控制样品的成分，我们沉积了Co/C多层膜。沉积后，我们对样品进行了退火热处理，得到了Co的细小颗粒。退火后的样品显示出较大的饱和磁化强度和矫顽力，但没有得到HCP-Co颗粒。我们推测这是由于热处理温度低于相变温度hcp-Co所致。总之，我们成功地控制了Co-C薄膜的成分，但没有得到hcp-Co的细小颗粒。除了通过引入多层结构和热处理获得了hcp-Co细小颗粒外，还可以得到hcp-Co微粉。

The magnetic properties of Co-C thin films deposited by laser ablation method were investigated. The structures of Co-C thin films were also investigated by X-ray diffractions.Co-C thin films were deposited onto glass substrates using composite Co-C target (Method 1). We also deposited Co-C thin films with the different geometry that Co and C targets were arranged separately (Method 2). The film thickness was 200Å-1000Å.Samples from Method 1 included Co fine particle. Saturation magnetization and coercivity were about 1200 emu/cc and 300 Oe. And we confirmed that the hcp Co particles were obtained. However, the average particle size estimated by X-ray diffraction peak was 26nm. We had no decrease the particle size in order to apply the Co-C thin films to magnetic recording media.In order to decrease the particle size we deposited Co-C films using Method 2 with annealing. As deposited samples had very small saturation magnetization and coercivity. It was indicated that the Co particle is very small. After annealing, saturation magnetization and coercivity increased. But we could not obtain the hcp Co particles. It was very difficult that the control of structure and composition using co-ablation.We deposited Co/C multilayer in order to control the sample composition strictly. After deposition, we annealed the samples to obtain the Co fine particles. Samples after annealing indicated large saturation magnetization and coercivity, but hcp Co particles were not obtained. We speculate that this is because the annealing temperature is less than the phase transition temperature hcp Co.In conclusion, we succeeded in control of the composition on Co-C thin films, but hcp Co fine particles were not obtained. We can except that the hcp Co fine particles were obtained with introducing the multilayerd structure and annealing.