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题名 超高密度磁记录介质用Fe-Pt薄膜的研究
姓名 曹江伟
院系 物理科学与技术学院
专业 凝聚态物理
学位名称 理学博士
外文题名 Studies of Fe-Pt Thin Films for Ultra-high Density Magnetic Recording Media
第一导师姓名 杨正
关键词 磁记录;薄膜;Fe-Pt;磁性;微结构
外文关键词 magnetic recording;thin film;Fe-Pt;magnetic properties;microstructure
学科 理学
摘要 由于超顺磁效应的限制,使用传统的CoCr基薄膜介质的硬磁盘系统记录潜力已经发挥到了极点,要想继续提高磁记录系统的记录面密度,必须探寻新的材料。本论文主要研究了FePt薄膜作为下一代垂直磁记录介质的可行性。由于化学有序的fct-FePt相具有高单轴磁晶各向异性能(7×107erg/cm3),允许把晶粒尺寸降低到几个纳米左右,同时保持足够的热稳定性,从而可以获得更小的记录信息单元,以实现更高的记录密度。 本论文主要围绕着两个问题展开:第一部分是致力于降低FePt和FePt-Al2O3薄膜中FePt相的有序化温度。由于FePt薄膜从fcc到fct相的转变温度为500℃~600℃,目前的磁盘生产线都不能承受如此高温,因此降低FePt相的有序化温度就变得非常重要。我们通过在溅射过程中添加N2和原位有序两种方法在一定程度上降低了FePt相的有序化温度,主要得到了以下结果: 1)溅射过程中添加15%的N2使FePt-Al2O3(15vol.%) 薄膜中FePt的有序化温度降低了100℃左右,并且薄膜的织构从原来的(111)织构转变为杂乱取向。结构分析表明热处理过程中N原子的释放在薄膜中形成了大量的空穴,这有利于FePt相的有序化。 2)原位有序制备的FePt薄膜其有序化温度可以降低到250℃左右,FePt-Al2O3(15vol.%)薄膜的有序化温度为400℃左右,这两个温度比热处理的方法的有序化温度低200℃左右。 3)400℃下沉积的FePt-Al2O3(15vol.%)薄膜中FePt的晶粒大小约为6nm左右,已经达到了超高密度垂直磁记录介质的要求,然而FePt晶粒大小分布需要进一步改善。 4)原位有序的FePt和FePt-Al2O3(15vol.%)薄膜的低温有序化和我们所使用的溅射装置的靶到基片的间距较小有关,从而低气压下被溅射的原子在到达基片时具有较高的能量,这部分能量有助于薄膜的低温有序化。 第二部分主要致力于制备垂直取向的FePt薄膜,讨论了它们作为垂直磁记录介质的可行性。由于垂直磁记录技术要求磁记录介质薄膜中晶粒的易磁化方向垂直于膜面,对于FePt薄膜来说,即具有(001)取向。我们在本论文中采用Cr(W)衬底层和[Fe/Pt]n多层两种方法制备了垂直取向的FePt薄膜,主要结论如下: 1)直接沉积在Cr(200)衬底上的FePt或FePtCu薄膜主要表现为(200)织构。 2)使用5nm的Mo中间层,有效地抑制了FePt层和Cr衬底层之间的扩散,FePt(20nm)/Mo(5nm)/Cr(80nm)薄膜的矫顽力高达9kOe,同时得到了较好的(001)择优取向的FePt薄膜。 3)在Cr衬底层中添加少量W元素实现了FePt层的织构从(200)向(001)转变,当衬底层中W含量为15at.%时,得到了较强的(001)织构的FePt薄膜。 4)在温度为500℃的基片上采用交替沉积的FePt薄膜表现出较强的(001)织构,当单层厚度为5nm,总厚度大于50nm,成分为Fe55Pt45的薄膜表现出最强的(001)织构,进一步热处理可以增强(001)织构。(001)织构的出现与起始层的织构及热处理过程中晶粒的长大有关。 5)[Pt(2.6nm)/Fe(2.4nm)]n薄膜中反磁化过程主要以畴...
外文摘要 The areal density of hard disk drive using traditional CoCr-based thin films media can not be elevated further because of the super-paramagnetism effect. In order to increase the areal density in magnetic recording system, the studies of new magnetic recording media materials are necessary. In this dissertation, we have studied the possibility of FePt thin films as ultra-high density perpendicular magnetic recording media. Due to its high uniaxial magnetocrystalline anisotropy (7×107erg/cm3), fct-FePt grains could be fined to nanometer-sized while remaining enough thermal stability. Therefore, lager areal density could be realized on these tiny grains. This dissertation focuses on two aspects. The first is the reduction of transforming temperature of FePt from fcc to fct phase in FePt or FePt-Al2O3 thin films. The actual hard disk manufacture line does not endure the temperature as higher as 500oC~600oC, which is necessary for FePt phase transforming from fcc to fct phase. Hence, the study on reducing the ordering temperature of FePt is very important. In this dissertation, the transforming temperature was reduced to a certain extent by the addition of N2 during sputtering and in-situ ordering. The main results are as follows: 1)15% N2 addition during sputtering can reduce the transforming temperature of FePt phase from fcc to fct phase about 100oC in FePt-Al2O3(15vol.%) thin films. The texture of FePt phase changes from (111) dominant texture to a more random texture due to the N2 addition. Structural analysis reveals that the release of N atoms during the post annealing induces a large number of vacancies in the films, which benefits to the transformation of FePt phase from fcc to fct. 2)The transforming temperature of the FePt films prepared by in-situ ordering is only 250oC, while 400oC for FePt-Al2O3(15vol.%) thin films. Both of the temperatures are 200 oC lower than that of the films prepared by post-annealing. 3)Fine FePt grains with 6nm average diameter were obtained in FePt-Al2O3(15vol.%) films deposited at 400 oC, which accords with the requirement for ultra-high density magnetic recording media. However, the grain size distribution needs to be improved further. 4)The lower ord...
研究领域 磁学与磁性材料
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