Ti衬底层对FePt颗粒膜的微结构和磁特性的影响

在室温下,应用对靶直流磁控溅射设备在普通玻璃基片上制备了FePt(30nm)/Ti(tnm)颗粒膜样品,随后,在真空中进行了原位退火.详细研究了Ti衬底层对FePt颗粒膜的微结构和磁特性的影响.X射线衍射图谱表明样品形成了较有序的L10织构,Ti和FePt形成了三元FePtTi合金.当Ti层厚度t=5 nm、退火温度Ta=500℃时,样品具有高度有序的L10织构、小的颗粒尺寸和优异的磁特性.矫顽力超过了6.7 kOe,饱和磁化强度为620emu/cc.并且具有较小的开关场分布.结果表明FePt/Ti颗粒膜系统可作为超高密度磁记录介质的候选者.     

Pt缓冲层厚度对FePt薄膜合金相转变和磁性能的影响

利用磁控溅射法制备了具有Pt缓冲层的[FePt]50多层膜.通过x射线衍射(XRD)分析和磁性测量研究了不同缓冲层厚度对样品微结构演变和磁性能的影响.结果表明,随着Pt缓冲层厚度(t≤8.6 nm)的增加,薄膜合金的有序化温度明显降低,晶粒尺寸逐渐减小FePt薄膜样品点阵常数c/a的比值逐渐减小,有序度参数S逐渐增大;同时样品的矫顽力也随着缓冲层厚度的增加而增大,在425℃退火的样品,其矫顽力由缓冲层厚度t=0时的398 kA/m增加到t=8.6nm时的523 kA/m(接近无缓冲层样品在500℃退火的值),平均变化率为14.53 kA·m-1/nm,有效地降低了样品的退火温度;与此同时,剩磁比逐渐减小,从0.68减少到0.56.     

FePt/Cu多层膜化降低L10-FePt有序化温度

采用直流磁控溅射方法制备FePt／Cu多层膜,再经不同温度下真空热处理得到有序L10-(FePt)100-xCux薄膜．结果表明,Cu的添加可以降低FePt薄膜有序化温度．[FePt(4nm)／Cu(0．2nm)10多层膜在350℃热处理1h后,有序度增至0．6,矫顽力达到421kA／m．对插入极薄Cu层促进有序化在较低的温度下进行的热力学和动力学因素进行了讨论.     

热处理对FePt纳米颗粒磁性能的影响

通过多重还原法制备FePt纳米颗粒,并研究不同热处理温度对其磁性能影响.XRD及TEM分析表明:所制备的FePt纳米颗粒为fcc结构,颗粒为类球形且分散性较好,尺寸在5.0 nm左右.DSC及VSM显示,高温退火处理可以使FePt纳米颗粒从无序的fcc相变成有序的fct相,随着温度的升高矫顽力变大,600 ℃时可达240 kA/m,但是在高温区(550 ℃及以上)矫顽力的变化并不明显,这主要是由高温退火过程中纳米颗粒的团聚导致的.     

界面散射对Ni80Co20／M（M=Co，Cr，Ag）多层膜各向异性磁电阻的影响

用磁控溅射方法制备了Ni80Co20/M(M=Co,Cr,Ag)多层膜样品系列,Co,Cr,Ag杂质层的标称厚度为0.1 nm,研究了界面散射对多层膜的磁及输运性质的影响.零场电阻率ρ的测量结果表明,对含Cr样品,p随杂质层间距L的依赖关系能较好的用Fuchs-Sondheimer(F-S)理论描述.而对含Co和Ag样品,ρ随L的依赖关系在L小于15 nm时开始偏离F-S理论.磁电阻测量表明,含Cr和Ag样品,各向异性磁电阻△ρ在L＜15 nm时随L的减小陡然下降.对含磁性Co元素的样品,其△p值在L＞15 nm时高于Ni80Co20单层薄膜的△ρ值;在L＜15 nm时△p值随L呈现振荡变化的趋势.磁性测量表明,三个系列样品的矫顽力Hc在L＜15 nm时都随L近似直线上升,在L＞15 nm后趋于饱和;经400℃真空退火后Hc都显著下降.     

[FePt/C]n多层膜的结构和磁学性能

采用磁控溅射方法制备FePt（50nm）和[FePt（2nm，3nm，5nm）／C（1nm）]。膜，并在550℃退火30min，研究了周期数（n）对FePt／C系列多层膜结构及磁学性能的影响。结果表明：退火后多层膜的矫顽力在总膜层厚度约为30nm时出现最大值；随着n的增大，多层膜的饱和磁化强度和晶粒尺寸均不断增大；C的加入可以有效降低晶粒间交换耦合作用。刚此可以通过控制周期数得到县仃合适的微观结构和高的磁学性能的FePt／C多层膜，从而满足超高密度磁记录介质的要求。     

FePt/Au多层膜的结构和磁性能研究

采用磁控溅射在SiO2<0001>基片上制备了FePt(2nm)/Au(tnm)多层膜,将其在不同温度下进行热处理。利用X射线荧光光谱仪、X射线衍射仪、振动样品磁强计和原子力显微镜对样品的结构和性能进行了研究。结果表明,沉积态样品具有超晶格结构,fccFePt和Au共格生长。经过较低温度热处理后,样品仍然保持超晶格结构。样品经400℃热处理后,开始发生有序化转变。经600℃热处理后,平行于膜面和垂直于膜面的矫顽力分别为811.7和829.2kA·m-1。当t=2.5nm时,最有利于L10-FePt相的形成。在磁化过程中,畴壁移动和磁矩转动机制共存。样品经热处理后,形成了均匀的薄膜。     

Ag中间层对FePd薄膜结构及磁性能的影响

采用磁控溅射方法在石英玻璃上制备了FePd(93 nm)单层膜和FePd(46.5 nm)/Ag(10 nm)/FePd(46.5 nm)多层膜,并在600℃退火不同时间,通过XRD、VSM对薄膜样品的结构和磁性能进行测量。结果发现:FePd单层膜在600℃退火240 min后有序化转变不明显,300 min后部分有序化,360 min后基本上完全有序化,形成了有序面心四方结构的L1_0-FePd相;当热处理时间为420 min时,有最大的面内矫顽力,约为1670 Oe;Ag中间层对溅射态的FePd薄膜衍射峰的形成有抑制作用,Ag中间层的添加可大幅缩短FePd有序化的时间;样品热处理5 min后就开始有序化,热处理15 min后样品性能即可达到最好,有最大的面内矫顽力2660 Oe,但热处理时间过长会使薄膜磁性能变差。     

磁场下电沉积制备CuCo颗粒膜的巨磁电阻效应

在磁场下电沉积制备CuCo功能膜材料,研究膜层的巨磁电阻效应及磁性能.应用X射线衍射仪(XRD)对镀层微观结构随热处理温度的变化进行分析,采用四引线法及振动样品磁强计(VSM)测量膜层的磁性能.磁阻测试发现:磁感应强度为0.6 T下制备的CuCo颗粒膜经500 ℃真空退火处理1 h后,其巨磁电阻值较无磁场下制备的提高约25%,这是由于0.6 T下制备的颗粒膜晶粒较致密,同时磁场减少了膜层内部缺陷,如杂质、夹杂等.样品磁滞回线表明:500 ℃真空退火处理1 h后膜层具有最佳的磁性能,此时膜层中的单磁畴磁性粒子有助于提高巨磁电阻值.CuCo颗粒膜电沉积制备过程中施加磁场可以改善膜层的微观结构,使其具有更高的巨磁电阻效应.     

共溅射与多层膜溅射制备FePt：Ag颗粒膜的微观结构比较

采用共溅射和多层膜溅射两种不同的溅射方式制备FePt：Ag颗粒膜。MFM和TEM微观结构观测的结果表明：与多层膜溅射制备的FePt：Ag颗粒膜相比，共溅射制备的颗粒膜具有更小的磁畴尺寸和晶粒尺寸，并且其磁畴和晶粒的分布更加均匀。这种微观结构上的区别可解释为共溅射制备的颗粒膜中Ag原子的分布更加具有随机性。对薄膜内部缺陷的研究进一步证实了该解释。     

（001）-oriented FePt/Ag composite films for perpendicular recording

FePt/Ag thin films were deposited by magnetron sputtering onto 7059 glass substrates, then were annealed at 550 ℃ for 30 min. Nanostructured FePt/Ag films were successfully obtained with the magnetic easy axis of L10 FePt perpendicular to the film plane. It was found that the development of (001) texture depended strongly on the thicknesses of FePt magnetic layer and Ag underlayer. The L10 ordered FePt(15 nm)/Ag(50 nm) with (001) orientation can be obtained. And the perpen-dicular coercivity of FePt(15 nm)/...     

Effect of Ti layer thickness on microstructure and magnetic properties of Ti/Co/Ti films

TiCoTi granular films were prepared by DC facing-target magnetron sputtering system onto glass substrates and subsequently in situ annealing in vacuum. Structural of Ti ( t nm)/Co (40 nm)/Ti ( t nm) films were investigated in detail, which shows that the majority Co nanograins are formed as the hexagonal-close-packed (HCP) structure. Vibrating sample magnetometer (VSM) and scanning probe microscope (SPM) were applied to study the magnetic properties, morphologies and domain structures of these samples. It has been found that the structure and magnetic properties of the Ti/Co/Ti films depend strongly on the Ti layer thickness. The out-of-plane coercivities ( Hc) of the film is maximum about 78.8 kA·m-1 when t =5 nm with annealing at 300 ℃; the distributing of grains of the sample is uniformity; and the average size of particles is about 13 nm. The obtained results suggest that this system is perpendicular anisotropy and might be applicable to perpendicular magnetic recording media.     

Microstructure and magnetic properties of Ti/Co/Ti films

The two series of as-deposited and annealed Ti/Co/Ti thin films were deposited by magnetron sputtering onto glass substrates at room temperature. The structural and magnetic properties of the films at room temperature were investigated as function of Co layer thickness. X-ray diffraction (XRD) profiles show Co nanograins are formed as the hexagonal-close-packed (hcp) structure. The perpendicular coercivity of the Ti(15 nm)/Co(30 nm)/Ti(15 nm) film annealed at 450 ℃ for 30 min is about 288 kA·m-1 .     

Effect of Ag（Ti） underlayers on CoCrPt thin film media

1　INTRODUCTIONMany works have been done in recent years onCo based granular alloys for potential applicationsas recording magnetic media[1 5]. The ideal granu lar media should consist of small and uniformgrains. High anisotropy magnetic grains embeddedin a robust non magnetic matrix are required. Highcoercivity, large squareness and negative nuclea tion field are very important for magnetic recordingfilms.The addition of Pt to the recording layer canincrease the anisotrop…     

Structural transformation of FePt nanocomposite films during annealing and its effects on magnetic properties

Fe100-xPtx(x=30at.%-60at.% ) nanocomposite films were deposited on natural-oxidized Si(100) substrates by magnetron sputtering. The as-deposited films were annealed between 373 and 1073 K. In situ X-ray diffraction shows that the FePt nanocomposite films undergo a phase transformation from a disordered FCC phase to an ordered L10 phase between 673 and 773 K. The coercivity is 306 kA·m-1 whiles the average grain sizes is about 10 nm in the optimized FePt alloy film sample annealed at 673K. The adjustable coercivity and fine grain size suggest that this FePt nanocomposites system is suitable as recording media at extremely high areal density.     

The effect of multilayer structure on magnetic properties of FePt thin films

The Fe/Pt multilayer films with different structures were deposited by RF magnetron sputtering on glass substrates, and the L1₀-FePt films were obtained after theas-deposited samples were subjected to vacuum annealing at various temperatures. Results show that the Fe/Pt multilayer structure can effectively reduce the ordering temperature of FePt film, and the in-plane coercivity of [Fe (5.2 nm)/Pt (5.2 nm)]₇ multilayers can reach 161.2 kA/m after annealed at 350 ℃ for 30 min. When Fe and Pt layer thickness is equal, the coercivity of the film is the largest. On the other hand, the different Fe-Pt crystalline phases such as Fe₃Pt and FePt₃ phases are formed after annealing when the thickness ratio of Fe/Pt deviates from 1 after annealing. When Fe and Pt have the same thickness, the thinner single layer gets the lower ordering temperature and the larger coercivity.     

Effect of Ni doping on the microstructure and magnetic properties of FePt films

FePtNi films with different Ni contents were deposited on glass substrates by RF magnetron sputtering, and the Llx-FePtNi films were obtained after the as-deposited samples were subjected to vacuum annealing. The magnetic properties, structures, and orientations of the Llx-FePt films with Ni doping were studied. The results show that with increasing Ni content, the (001) peak position of the FePtNi films shifts to a higher angle in comparison with FePt. which suggests that there is partial Ni substitution in the Ll0 lattice. The perpendicular coercivity decreases from 661 to 142 kA/m and magnetization decreases from 512 to 433 kA/m with increasing Ni content. In comparison with FePt films, the FePtNi films can effectively reduce the Curie temperature, which makes FePtNi fdms promising media candidates in thermally assisted recording (TAR).     

Magnetron sputtering deposition of [FePt/Ag]n multilayers for perpendicular recording

[FePt/Ag]n multilayers were deposited on glass substrates by RF magnetron sputtering and ex situ annealed at 550℃ for 30 min. The effects of inserted Ag layer thickness and the number of bilayer repetitions （n） on the structure and magnetic properties of the multilayers were investigated. It was found that the difference between in-plane and out-of-plane coercivities varied with an increase of inserted Ag layer thickness in the [FePt 2 nm/Ag x nm]10 multilayers. The ratio of out-of-plane coercivity to in-plane coercivity reached the maximum value with the Ag layer thickness of 5 nm, indicating that the Ag layer thickness plays an important role in obtaining perpendicular orientation. For the [FePt 2 nm/Ag 5 um]n multilayers, perpendicular orientation is also influenced by n. The maximum value of the ratio of out-of-plane coercivity to in-plane coercivity appeared when n was given as 8. It was found that the [FePt 2 nm/Ag 5 nm]8 had a high perpendicular coercivity of 520 kA/m and a low in-plane one of 88 kA/m, which shows a strong perpendicular anisotropy.