Perpendicular Exchange Coupling in TbFeCo/FePt Bilayer Films

We investigate the structure and exchange coupling in TbFeCo/FePt bilayer films. It is found that FePt has the L10 structure and the easy axis of the FePt film is perpendicular to the film plane. Results of the vibrating sample magnetometer and the magneto-optical Kerr effect measurements show a strong perpendicular exchange coupling between the ferrimagnetic TbFeCo layer and the hard ferromagnetic FePt layer. The magnetization direction of each layer and the process of magnetization reversal are discussed in detail. The switching field dependence on the exchange coupling has been modelled by micromagnetic simulation and the interlayer coupling constant is about -0.9 erg/cm^2 according to this simulation.     

The influence of interface exchange coupling on the demagnetization process for perpendicularly oriented FePt/α-Fe/FePt trilayers

The influence of the interface exchange coupling on the magnetization reversal process for a FePt/α-Fe/FePt tri-layer structure has been studied through a micromagnetic approach.The analytical formula of the nucleation field has been derived.It is found that the nucleation field increases as the interface coupling constant rises.Especially when the thickness of the soft layer is small,the influence of the exchange coupling on the nucleation field is significant.The angular distributions of the magnetization for various exchange coupling constants have been obtained by numerical calculation.It is found that the angular distribution of the magnetization is discontinuous at the interface of the hard and soft layers.In the meantime,the pinning field decreases with the increase of the thickness of the soft layer and the exchange coupling constant.     

Comparative evaluation of performance of percolated perpendicular media using FePt–MgO/Pt/Cr trilayer and FePt–MgO/MgO bilayer

(Fe₄₈Pt₅₂)_100−x–(MgO)_x films were used to examine the performance of a perpendicular percolated medium. Two underlayers, Pt(0 0 1)/Cr(0 0 2) and MgO(0 0 2), were used for comparison. The (Fe₄₈Pt₅₂)_100−x–(MgO)_x film with the MgO underlayer exhibits a strong preference to segregate at FePt grain boundaries. The microstructure with small closely packed MgO particles (2–4 nm) dispersed uniformly in the L1₀ FePt matrix was achieved in the Pt/Cr underlayered sample. Structural data reveal that the precipitate is crystallographically coherent with the surrounding L1₀ FePt phase and preserves good lattice alignment. Magnetic results indicate significant pinning behavior for those introduced non-magnetic columns with an enhanced coercivity of about 70%—much greater than that of the MgO underlayered samples. Percolated perpendicular medium can be realized in the FePt system and a Pt(0 0 1)/Cr(0 0 2) underlayer promotes the formation of pinning sites within the FePt grains.     

磁控溅射方法制备垂直取向FePt/BN颗粒膜

用磁控溅射在热单晶MgO(100)基片上制备了［FePt/BN］多层膜，经真空热处理后，得到具有垂直取向L1₀-FePt/BN颗粒膜.X射线衍射结果和磁性测量的结果表明，［FePt(2nm)/BN(0.5nm)］₁₀和［FePt(1nm)/BN(0.25nm)］₂₀多层膜经700℃热处理1h后，均具有较好的(001)取向.［FePt(1nm)/BN(0.25nm)］₂₀垂直矫顽力达到522kA/m，剩磁比达到0.99，开关场分布S达到0.94，FePt晶粒平均尺寸约15—20nm，适合用于将来超高密度的垂直磁记录介质. 关键词： 磁控溅射 垂直磁记录 0-FePt/BN纳米颗粒膜')" href="#">L1₀-FePt/BN纳米颗粒膜     

FePt薄膜中磁相互作用

采用磁控溅射方法在自然氧化的单晶Si(100)衬底上制备了纳米结构的Fe₅₃Pt₄₇薄膜，并研究热处理后薄膜中的磁相互作用、晶粒尺寸与热处理温度的关系.经400℃热处理后，FePt薄膜中有明显的面心四方相形成，薄膜表现出硬磁性，晶粒尺度在20 nm，薄膜内部存在软硬磁交换耦合作用；随着热处理温度升高，硬磁相含量增加.同时由于FePt薄膜的晶粒长大，部分软硬磁晶粒之间的交换耦合作用失效；600℃热处理后，FePt的面心立方相已经完全转变为面心四方相，薄膜矫顽力由硬磁相之间的静磁作用贡献. 关键词： 磁性薄膜 纳米晶 磁性能 热处理     

垂直取向FePt/Ag纳米颗粒薄膜的结构和磁性

用磁控溅射法在单晶MgO(100)基片上制备了［FePt 2 nm/Ag dnm］₁₀多层膜， 经真空热处理后，得到具有高矫顽力的垂直取向L1₀-FePt/Ag颗粒膜.x射线衍射结 果表明，在250 ℃的热基片上溅射，当Ag层厚度d=3—11 nm时，FePt颗粒具有很好的［001］取向，随着Ag层厚度的增加，FePt颗粒尺寸减小.［FePt 2 nm/Ag 9 nm］₁₀经过6 00 ℃真空热处理15 min后，颗粒大小仅约8 nm，垂直矫顽力达到692 kA/m.这种无磁耦合作用的颗粒膜，适合用作超高密度的垂直磁记录介质. 关键词： 磁控溅射 垂直磁记录 纳米颗粒膜 0-FePt/Ag')" href="#">L1₀-FePt/Ag     

Nanocomposite L10 FePt–SiNx and FePt–SiNx–C films with large coercivity and small grain size on a TiN intermediate layer

FePt–SiN_x–C films with high coercivity, (001) texture and small grain size were obtained by co-sputtering FePt, Si₃N₄ and C on TiN/CrRu/glass substrate at 380 °C. Without C doping, FePt–SiN_x films with good perpendicular anisotropy and a single layer structure were obtained. However, the grain size was still too large and the grain isolation was poor. When C was doped into the FePt–SiN_x films, the out-of-plane coercivity increased due to the decrease of the exchange coupling. In addition, the grain size of the FePt films decreased, and well-separated FePt grains with uniform size were formed. The microstructure of [FePt–SiN_x 40 vol%]−20 vol% C films changed from a single layer structure to a multiple layer structure when the FePt thickness was increased from 4 to 10 nm. By optimizing the sputtering process, the [FePt (4 nm)–SiN_x 40 vol%]−20 vol% C (001) film with coercivity higher than 21.5 kOe, a single layer structure, and small average FePt grain size of 5.6 nm was obtained, which makes it suitable for ultrahigh density perpendicular recording.     

利用FePt/Au多层膜结构制备垂直磁记录L10-FePt薄膜

利用磁控溅射方法在100℃的MgO单晶基片上制备了[FePt/Au]10多层膜,并研究了采用FePt/Au多层膜结构对FePt薄膜的有序化温度、矫顽力(HC)、垂直磁各向异性、晶粒尺寸以及颗粒间磁交换耦合作用的影响.磁性测试结果表明:FePt/Au多层膜在退火后具有较高的HC、良好的垂直磁各向异性、较小的晶粒尺寸且无磁交换耦合作用.截面高分辨电镜分析表明:Au可以缓解MgO和FePt之间较大的晶格错配,从而促进薄膜的垂直磁各向异性;同时,采用FePt/Au多层膜结构增加了FePt/Au界面能、应力能以及Au原子在薄膜中的扩散作用,促进了薄膜的有序化,从而有效降低了有序化温度,并且大幅度提高其HC.此外,Au原子部分扩散到FePt相的边界处,起到抑制FePt晶粒生长、隔离FePt颗粒的作用,从而显著降低了FePt晶粒的尺寸和颗粒间磁交换耦合作用.     

Bi底层对FePt薄膜的影响

利用磁控溅射的方法，在玻璃基片上制备了以Bi为底层的FePt薄膜，经不同温度真空热处理得到L1₀-FePt薄膜.研究了Bi做底层对FePt薄膜的有序化温度及矫顽力H_c的影响.实验结果表明：以Bi做底层的FePt薄膜在350℃实现低温有序，同时其H_c也有大幅度提高，并且可以在更大成分范围内获得H_c较高的L1₀-FePt薄膜.利用X射线光电子能谱研究了薄膜中Bi原子的分布情况，利用X射线衍射研究了薄膜的晶体学结构变化.结果表明,Bi底层在退火过程中的扩散促进了FePt薄膜有序度的升高. 关键词： 0-FePt薄膜')" href="#">L1₀-FePt薄膜 有序化温度 底层 扩散     

利用FePt/Au多层膜结构制备垂直磁记录L10-FePt薄膜

利用磁控溅射方法在100℃的MgO单晶基片上制备了［FePt/Au］₁₀多层膜,并研究了采用FePt/Au多层膜结构对FePt薄膜的有序化温度、矫顽力（H_C）、垂直磁各向异性、晶粒尺寸以及颗粒间磁交换耦合作用的影响.磁性测试结果表明：FePt/Au多层膜在退火后具有较高的H_C、良好的垂直磁各向异性、较小的晶粒尺寸且无磁交换耦合作用.截面高分辨电镜分析表明：Au可以缓解MgO和FePt之间较大的晶格错配,从而促进薄 关键词： 0-FePt薄膜')" href="#">L1₀-FePt薄膜 有序化温度 垂直磁各向异性 磁交换耦合作用     

c轴垂直取向FePt薄膜的磁和磁光性能研究

采用直流磁控溅射的方法在氧化镁(100)单晶基板上生长了一系列c轴垂直取向的FePt薄膜，通过改变沉积时的基板温度，薄膜从Fe，Pt原子无序排列的面心立方结构逐渐变化到有序排列的L1₀相面心四方结构.在此基础上，系统研究了FePt薄膜的化学有序度对磁和磁光性能的影响.随着有序度的增加，FePt薄膜的磁晶各向异性能，以及沿垂直方向的矫顽力、剩磁比均增加，在基板温度高于530 ℃时制备的薄膜中的磁晶各向异性能超过1 J/cm³.同时，还观察到有序FePt合金薄膜的磁光克尔光谱(克尔转角的大小和极值所对应的跃迁光子能量)随化学有序度的显著变化. 关键词： FePt薄膜 化学有序度参数 磁光克尔光谱     

室温生长MgO底层诱导(001)取向FePt薄膜的有序化过程对FePt成分的依赖

室温下通过磁控溅射在表面热氧化的Si基片上生长了MgO/Fe_xPt_100-x双层膜和Fe_xPt_100-x单层膜系列样品，Fe_xPt_100-x的原子成分x=48—68.研究了热处理前后不同成分FePt薄膜的晶体结构和磁性的变化，尤其是MgO底层的引入对FePt的晶体结构和磁性的影响 关键词： FePt(001)薄膜 0相')" href="#">L1₀相     

Reduced-temperature ordering of FePt nanoparticle assembled films by Fe30Pt70/Fe3O4 core/shell structure

In this paper, Fe30Pt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polyethylenimine （PEI）-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly technique. The dimension of core/shell structured nanoparticles was that of 4nm core and 2 nm shell. After annealing under a flow of forming gas （50%Ar2＋30%H2） for 1 h at or above 400℃, the iron oxide shell was reduced to Fe and diffused to Pt-rieh core, which leaded to the formation of L1. phase FePt at low temperature. The x-ray diffraction results and magnetic properties measurement showed that the chemical ordering temperature of Fe30Pt70/Fe3O4 core/shell nanoparticles assembly can be reduced to as low as 400℃. The sample annealed at 400℃ showed the eoereivity of 4KOe with the applied field of 1.5T. The core/shell structure was suggested to be an effective way to reduce the ordering temperature obviously.[第一段]     

L10相FePt纳米颗粒及其纳米结构研究进展

面心四方结构（L10相）的FePt复合纳米磁性颗粒具有极高的磁晶各向异性能、高饱和磁化强度、极小的超顺磁极限颗粒尺寸和优异的化学稳定性, 是下一代超高密度垂直磁记录介质最有希望的候选材料,在药物定向载体、纳米检测和敏感器件、功能化细胞研究等方面也有广泛的应用前景.文章概述了基于化学热溶剂分解方法制备FePt纳米颗粒、结构、性质,总结并评述了其在纳米结构自组装和应用等方面研究的最新进展.     

[(Fe/Pt/Fe)/Ag]n多层膜低温合成分离的L10相FePt纳米颗粒

制备了[(Fe/Pt/Fe)/Ag]n多层膜,研究了不同温度退火后的微结构和磁特性.实验结果表明温度高于400℃退火后,样品开始形成L10相的FePt纳米颗粒与Ag基体的复合结构.△M曲线的测量表明FePt颗粒之间不存在交换作用,非常清楚地说明非磁基体Ag有效地隔离了FePt磁性颗粒.有序相的低温合成可能和多层膜结构所造成的界面扩散以及Ag层引入的界面缺陷有关,同时,Ag原子较强的迁移性以及FePt与Ag之间表面自由能的显著差异,使FePt纳米颗粒被Ag隔离.     

C掺杂FePt铁磁薄膜光诱导超快退磁动力学研究

FePt合金薄膜由于具有较强的磁各向异性而在磁信息和磁光信息存储中具有重要的应用.C掺杂可精确调控薄膜的磁各向异性,从而可有效地改变薄膜的矫顽场.通过超短激光脉冲与铁磁薄膜相互作用,可以获得非平衡状态下电子、自旋和晶格等自由度之间的动态耦合参数,这是研究超快磁记录材料的物理基础.本文基于瞬态磁光Kerr效应,研究了两种C掺杂浓度下FePt薄膜的超快磁光响应.实验结果表明:瞬态Kerr信号与外加磁场正相关,磁场反向,Kerr信号反号,而瞬态反射率与外加磁场无关;不同C掺杂的FePt薄膜的矫顽场不同,软磁的退磁时间显著小于硬磁薄膜的退磁时间.我们还观测到超快激光在铁磁薄膜中诱导频率约为49 GHz的相干声学声子,该声子的频率与外加磁场无关.实验结果为设计和研制新型磁光薄膜提供了实验依据.     

[(Fe/Pt/Fe)/Ag]n多层膜低温合成分离的L10相FePt纳米颗粒

制备了［（Fe/Pt/Fe）/Ag］n多层膜,研究了不同温度退火后的微结构和磁特性.实验结果表明温度高于400℃退火后,样品开始形成L10相的FePt纳米颗粒与Ag基体的复合结构.ΔM曲线的测量表明FePt颗粒之间不存在交换作用,非常清楚地说明非磁基体Ag有效地隔离了FePt磁性颗粒.有序相的低温合成可能和多层膜结构所造成的界面扩散以及Ag层引入的界面缺陷有关,同时,Ag原子较强的迁移性以及FePt与Ag之间表面自由能的显著差异,使FePt纳米颗粒被Ag隔离. 关键词： L10相 FePt 交换作用     

Quasi-Hexagonal Ordered Arrays of FePt Nanoparticles Prepared by a Micellar Method

Hexagonally ordered arrays of magnetic FePt nanoparticles on Si substrates are prepared by a self assembly of diblock copolymer PS-b-P2VP in toluene, a dip coating process and finally plasma treatment. The as-treated FePt nanoparticles are covered by an oxide layer that can be removed by a 40 s Ar＋ sputtering. The effects of the sequence of adding salts on the composition distribution are revealed by x-ray photoelectron spectroscopy measurements. No particle agglomeration is observed after 600℃annealing for the present ordered array of FePt nanoparticles, which exhibits advantages in patterning FePt nanoparticles by a micellar method. Moreover, magnetic properties of the annealed FePt nanoparticles at room temperature are investigated by a vibrating sample magnetometer.     

CoPt(FePt)-C纳米复合膜的结构与磁性

用磁过滤脉冲真空电弧沉积方法制备了CoPt(FePt) C纳米复合薄膜，并在不同温度下进行了退火处理，研究了薄膜中碳的含量以及退火温度对薄膜结构与磁性能的影响.制备态薄膜经过足够高的温度退火后，x射线衍射和磁力显微镜分析发现，在碳基质中生成了面心四方相的CoPt(FePt)纳米颗粒.对于特定组分为Co24Pt31C45和Fe43Pt35C22的薄膜，矫顽力以及颗粒尺寸都随退火温度的升高而增大，当退火温度为700℃时，Co24Pt31C45薄膜的矫顽力为21×105A/m，晶粒尺寸为17nm;当退火温度为650℃时，Fe43Pt35C22相应值分别为28×105A/m和105nm. 关键词： 磁记录材料 磁性薄膜 CoPt FePt纳米复合薄膜