退火效应对非晶TbFeCo薄膜磁性能的影响

详细研究了退火效应对非晶TbFeCo薄膜磁滞回线的影响。 10 0℃退火表明 ,薄膜保留较大的垂直磁各向异性、矫顽力和很好的矩形比 ,磁致伸缩各向异性是引起矫顽力下降的主要原因。经 13 0℃退火显示 ,矫顽力和垂直磁各向异性明显下降 ,薄膜仍展示垂直于膜面的矫顽力和磁滞回线 ,但是薄膜显示一清晰的平面内磁各向异性。实验表明 ,矫顽力和垂直磁各向异性的大大降低只是与退火温度的升高有关 ,而长时间的退火并不能有效影响薄膜的磁性和矫顽力。     

真空退火Co/Pt多层膜的结构、磁及磁光特性分析

本文用直流磁控溅射方法制备了Co／Pt多层膜,并对其进行了较为细致的真空退火处理,结果表明,适度的低温退火可增加Co／Pt多层膜的矫顽力,而并不削弱其磁滞克尔回线的矩形特征．当退火温度达到300℃以后,Co／Pt多层膜的矫顽力、垂直各向异性和克尔角将强烈下降,晶体结构的改善及应力的释放、晶粒的增长、层间原子扩散引起的Co层有效厚度减薄,进而居里温度的下降,分别是Co／Pt多层膜在低温、中温、高温退火过程中,磁及磁光性能变化的主要机制．     

Pt/(Pt/Co)n/FeMn/Pt多层膜中Pt插层对交换偏置场的影响

在具有垂直磁各向异性Pt／（Pt／Co）n／FeMn／Pt多层膜中的Co／FeMn界面插入极薄的Pt层时，其交换偏置场有明显提高。研究结果表明：由于在Co／FeMn界面存在界面反应，破坏了（Pt／Co）n多层膜中靠近FeMn层的Co层的垂直磁各向异性，导致垂直交换偏置场Hex减弱。当在（Pt/Co）n与FeMn界面之间插入Pt层时可以有效地阻止这一反应发生，从而提高了多层膜的垂直交换偏置场Hex。     

CoSiB/Pt多层膜垂直磁各向异性及热稳定性

采用磁控溅射方法在单面附有300 nm SiO2的单晶硅基片上制备了以Pt为底层的CoSiB/Pt多层膜样品.CoSiB/Pt层周期数确定为2,对样品底层厚度及周期层厚度进行调制,根据反常霍尔效应系统地研究了CoSiB/Pt多层膜垂直磁各向异性(perpendicular magnetic anisotropy,PMA)及薄膜的热稳定性.通过对这些参数的调节获得了具有良好垂直磁各向异性的最佳多层膜样品结构Pt(1)/[CoSiB(0.5)/Pt(1)]2,底层Pt和周期层中CoSiB,Pt的最佳厚度分别为1,0.5 nm和1 nm.对最佳样品进行XRD图谱分析,磁滞回线测量以及一系列退火处理.结果表明,样品具有明显的(111)CoPt衍射峰,形成了较好的(111)织构,界面耦合增强,结晶度较好,计算出样品的有效磁各向异性常数Keff达到5.11×104 J·m-3,样品具有良好的PMA;当退火温度为200℃时,样品的CoPt(111)峰强度显著增强,界面形成了较强的(111)织构,Keff达到最大值1.0×105J·m-3,当退火温度不超过400℃时,样品仍能保持良好的PMA.多层膜样品结构Pt(1)/[CoSiB(0.5)/Pt(1)]2具有良好的PMA和热稳定性,且合适的退火温度有利于提高样品的PMA.     

NaBH4对化学镀CoFeB薄膜的制备和磁性能的影响

利用化学镀方法制备了CoFeB薄膜。研究了还原剂硼氢化钠NaBH4浓度对薄膜沉积速率、成分、结构和磁性能的影响。发现随着NaBH4浓度增大,沉积速率先升高后降低;CoFeB薄膜的结构由晶态转变为非晶态;Co、Fe析出量下降,析出B量增大;饱和磁化强度Ms减小,矫顽力Hc降低;CoFeB薄膜中的非晶磁性来源是由于近邻原子间的交换作用和局域磁各向异性这种短程有序确定的。     

L10相CoPt纳米磁性材料的研究进展

综述了低维CoPt纳米磁性材料的制备方法(液相法、电化学沉积法和物理气相沉积法)。L10相CoPt纳米磁性材料因其强烈的单轴磁晶各向异性和高的矫顽力成为当前研究的热点,分析了影响L10相CoPt磁性材料的成相因素如退火、基底等,并系统总结了提高磁性能的方法,展望了其研究趋势。     

Cr底层对DyCo薄膜磁性能与结构影响研究

采用磁控溅射法制备了DyCo/Cr非晶垂直磁化膜.振动样品磁强计(VSM)测试结果显示,有无Cr底层的DyCo薄膜都具有垂直磁各向异性,加入Cr底层能将DyCo薄膜的矫顽力从163kA/m提高到290kA/m.薄膜断面扫描电镜(SEM)照片可以看出,Cr底层能够诱导上层的DyCo薄膜形成柱状结构.这一柱状结构导致了薄膜矫顽力的提高.     

流动式单电解槽电结晶制[Co/Pt]n(n≥200)金属多层膜的研究

采用电化学结晶的方法，在硼酸系流动式单电解槽中成功制得[Co／Pt]200多层膜。通过低角度X射线衍射(LXRD)证实了多层膜结构的存在．中角度X射线衍射(MXRD)则证明了Co—Pt界面上有CoPt3化合物的存在．首次确认了用电结晶法所得的[Co／Pt]n多层膜中存在CoPt3化合物的事实。     

退火处理Fe(Co)Al(Zr)O系薄膜磁性能的研究

采用射频磁控溅射装置在氩气氛下制备了Fe(Co)Al(Zr)O系薄膜.用X射线衍射仪、透射电镜及其选区衍射来分析薄膜的微结构.用振动样品磁强计、磁导计等测量了矫顽力Hc、饱和磁化强度Ms及磁导率等磁性参数.通过退火处理研究了Fe(Co)Al(Zr)O系薄膜的磁性能.Fe(Co)Al(Zr)O系薄膜磁各向异性是由形状各向异性引起的.     

溅射工艺条件对TbFeCo/Pt薄膜磁性能的影响

采用射频磁控溅射法在玻璃基片上成功制得了TbFeCo/Pt非晶垂直磁化膜,系统研究了溅射工艺参数对TbFeCo薄膜磁性能的影响.振动样品磁强计测量结果表明:Tb含量在补偿成分点附近,采用较低的溅射氩气压与Pt底层,有利于提高TbFeCo薄膜的磁性能;当Tb含量为0.24,溅射功率为300W,溅射气压为0.53Pa,薄膜厚度为140nm时,TbFeCo/Pt薄膜矫顽力达到476kA/m,饱和磁化强度为151kA/m,剩磁矩形比超过0.8,该薄膜有望用作高密度光磁混合记录介质.     

Structural and magnetic properties of nanogranular Co-Pt/C films

The structural and magnetic properties of Co-Pt/C nanocomposite films were investigated as functions of Pt and C concentration, respectively. Under the same conditions two series multilayer samples with different Pt and C concentrations were prepared. The as-deposited films are amorphous Co-Pt-C alloys and magnetically soft. All samples were annealed in vacuum. The lattice structure is observed to transform and grain size is reduced to 7 nm. These structural transitions are accompanied by large changes in magnetic anisotropy. A maximum coercivity of approximately 5.4 kOe is obtained and a shoulder in hysteresis loops develops. These results show that Co-Pt particles are transformed by annealing from a disordered phase to ordered face-centered-cubic CoPt₃ and face-centered-tetragonal CoPt, commixed in a C matrix, and the various Co-Pt crystalline particles interact.     

Thickness dependence of microstructures and magnetic properties for CoPt/Ag nanocomposite thin films

Ag underlayer (30 nm) has improved the degree of ordering and perpendicular magnetic anisotropy of CoPt films (7.5-10 nm). After annealing at 600 °C and 700 °C, the perpendicular coercivity of CoPt/Ag films has been raised as the thicknesses of CoPt layers are increased. The magnetic easy axis of CoPt/Ag films would change from a random orientation to an out-of-plane orientation. It is found that Ag underlayer with thickness of 30 nm can improve the perpendicular magnetic properties of CoPt layers with thicknesses in the range of 7.5-10 nm. The CoPt/Ag films would be a candidate for perpendicular magnetic recording media.     

Magnetic properties and microstructures of sputtered epitaxial Co-rich Co-Pt films

Co₃Pt films of various thicknesses were deposited on Pt underlayers by conventional sputtering in order to investigate the effects of Pt underlayers and annealing temperatures on their microstructure and the magnetic properties. XRD and HRTEM analyses reveal perpendicular magnetic anisotropy in films of good epitaxial growth of Co₃Pt (002) on the Pt (111) underlayer when annealed at 300 °C. However, Pt atoms in the Pt underlayer will diffuse seriously into the Co₃Pt layer when the annealing temperature is increased to 375 °C. This changes the compositions to approach equiatomic CoPt, and shows in-plane magnetic anisotropy with soft magnetic properties.     

Effect of Ag underlayer on microstructures and perpendicular magnetic properties of CoPt nanocomposite thin films

CoPt/Ag films were prepared by magnetron sputtering on glass substrates and subsequent annealing. The dependence of degree of ordering and magnetic properties on Ag film thickness and annealing conditions were investigated. It was found that the Ag underlayer played a dominant role in inducing the (001) texture of the CoPt film after annealing. CoPt films with a thickness about 20 nm and Ag underlayers with a thickness about 70 nm are easy to obtain a large degree of ordering and a perpendicular magnetic anisotropy after annealing at 700 degrees C for 30 min. CoPt/Ag films with out-of-plane coercivity (Hc (perpendicular)) in the range of 13.5-14.0 kOe and a out-of-plane squareness (S(perpendicular)) of 0.97 were obtained after annealing at 700 degrees C for 30 min. Ag underlayer is beneficial to enhance the Hc(perpendicular)and S(perpendicular) of CoPt film significantly. The degree of ordering and perpendicular magnetic properties of the CoPt films which deposited on Ag underlayer are larger than those of the single layer CoPt films.     

Annealing behaviour and magnetic properties of Co/Pt and Fe/Pt bilayer thin films

The annealing behaviour and magnetic properties of Co/Pt and Fe/Pt bilayer thin films are investigated. The coercivity of Co/Pt bilayer thin films increases with annealing above 450 °C and shows a peak value of 40 kA m⁻¹ in the range from 500 to 550 °C. This increase is due to both the formation of a CoPt solid solution and the optimization of grain diameters. Furthermore, the increase is promoted by multilayering. Similar results were obtained for Fe/Pt bilayer thin films.     

Correlation of interlayer diffusion with the stoichiometric composition of RF sputtered Pt/Co/Pt sandwiched structures

Sandwiched structures comprising Pt/Co/Pt layers with varying cobalt deposition time was studied and its importance on the alloy composition, by correlating the effective interlayer diffusion with the atomic stoichiometry, has been presented. A structural phase transition from ordered L1₂ CoPt₃ –? L1₀ CoPt –? L1₂ Co₃Pt was observed with increasing Co deposition time after annealing at 700 °C. The cross-sectional SEM image of the as-deposited film clearly shows a cobalt layer sandwiched between platinum layers. Rutherford back scattering (RBS) analysis shows a multipeak signature for the as-deposited films. A detailed RBS investigation on the extent of interatomic diffusion reveals an equiatomic composition for 20 and 30 min deposition time after annealing. The equiatomic CoPt phase shows a magnetically hard behaviour with a maximum coercivity of 15000 Oe. The reported dependence of (BH)_max on coercivity concludes that by tailoring an additional parameter of deposition time, diverse combinations of structural and magnetic properties can be achieved for appropriate practical applications.     

Effect of capped layer on microstructure and magnetic properties of FePt films

Sputter-deposited FePt films exhibit an in-plane magnetic anisotropy when MgO is used as the capped layer. The perpendicular magnetic anisotropy of FePt films can be enhanced by introducing a Ag capped layer instead of a MgO capped layer. Although the in-plane coercivity (Hc_//) of FePt films decreases slightly after introducing a Ag capped layer instead of a MgO capped layer, the perpendicular coercivity (Hc_⊥) is increased significantly from 3169 Oe to 6726 Oe. Auger electron spectroscopy analysis confirms that Ag atoms diffuse from the capped layer into the FePt magnetic layer and are mainly distributed at the grain boundary of FePt. This phenomenon results in enhancement of the grain boundary energy and inhibition of grain growth, thus increasing the perpendicular coercivity and reducing the grain size of the FePt film.     

Effect of Pt content on structure and magnetic properties of Fe100−xPtx films deposited on thermally oxidized Si substrates by rapid thermal annealing

Fe_100-xPt_x films with Pt contents (x) = 29–65 at.% were deposited directly onto thermally oxidized Si(100) substrate by dc magnetron sputtering. The films were then post-annealed at 700 °C for 3 min by rapid thermal annealing (RTA) at a high heating ramp rate of 100 °C/s. Experimental results show that Fe₃Pt film displayed (111) preferred orientation and tended towards in-plane magnetic anisotropy when the Pt content was 29 at.%. When the Pt content was increased to 49 at.%, the FePt film inclined towards (001)-texture and perpendicular magnetic anisotropy. Its out-of-plane coercivity (Hc_⊥), saturation magnetization (M_s) and out-of-plane squareness (S_⊥) reached 1010 kA/m, 0.47 T and 0.8, respectively. These results reveal its significant potential as perpendicular magnetic recording media for high-density recording. Upon further increasing the Pt content to 65 at.%, the coercivity of the films decreased drastically to below 65 kA/m and tended towards in-plane magnetic anisotropy.     

High coercivity in nanostructured Co-ferrite thin films

Three methods including sol-gel, rf sputtering and pulsed laser deposition (PLD) have been used for the fabrication of high coercivity Co-ferrite thin films with a nanocrystalline structure. The PLD method is demonstrated to be a possible tool to achieve Co-ferrite films with high coercivity and small grain size at low deposition temperature. High coercivity, over 10 kOe, has been successfully achieved in Co-ferrite films with a thickness of ∼ 100 nm deposited using PLD with a substrate temperature at 550°C. The Co-ferrite films prepared by PLD at over 300°C on different substrates including amorphous glass, quartz and silicon exhibits an obvious (111) textured structure and possesses perpendicular anisotropy. Our study has also shown that the high coercivity is related with a large residual strain, which may induce an additional magnetic anisotropy (stress anisotropy) and at the same time serve as pinning centres, which can restrict the domain wall movement and therefore, increase the coercivity.