Microstructures of NiFe/nonmagnetic metal spacer/FeMn films and their influences on exchange coupling

The discovery of the oscillatory exchange coupling between ferromagnetic (FM) layers separated by a nonmagnetic spacer layer in 1986[1] aroused peoples interest in the magnetic prop-erties of metallic multilayered films. FM/ nonmagnetic metal spacer /FM systems with any of the 3d transition metals Fe, Co and Ni or their alloys as FM material have been systematically stud-ied[24]. Oscillatory exchange coupling via spacers has been known as a general phenomenon relevant to many spacer materi…     

Interface chemical states of NiO/NiFe films and their effects on magnetic properties

Ta/NiOx/Ni81Fe19/Ta multilayers were prepared by rf reactive and dc magnetron sputtering. The exchange coupling field ( Hex) and the coercivity ( Hc) of NiOx/Ni81Fe19 as a function of the ratio of Ar to O2 during the deposition process were studied. The composition and chemical states at the interface region of NiOx/NiFe were also investigated using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that the ratio of Ar to O2 has great effect on the nickel chemical states in NiOx film. When the ratio of Ar to O2 is equal to 7 and the argon sputtering pressure is 0.57 Pa, the x value is approximately 1 and the valence of nickel is + 2. At this point, NiOx is antiferromagnetic NiO and the corresponding Hex is the largest. As the ratio of Ar/O2 deviates from 7, the exchange coupling field ( Hex) will decrease due to the presence of magnetic impurities such as Ni +3 or metallic Ni at the interface region of NiOx/NiFe, while the coercivity ( Hc) will increase due to     

Perpendicular exchange bias of (Pt/Co)_n/FeMn multilayers

(Pt/Co)n/FeMn multilayers with perpendicular anisotropy (PA) were prepared by magnetron sputtering with Pt as the buffer layer and the capping layer. The dependence of perpendicular exchange bias (PEB), Hex, on the thickness of the FeMn antiferromagnet (AFM) layer is similar to that of in-plane exchange bias. The value of Hex for the (Pt/Co)3/FeMn multilayer reaches 22.3 kA/m. A thin Pt spacer was inserted between the Co/FeMn interface to enhance PEB. The PEB reaches the largest at 39.8 kA/m when the thickness of the Pt spacer is 0.4 nm.     

Perpendicular exchange bias of （Pt/Co）n/FeMn multilayers

(Pt/Co)n/FeMn multilayers with perpendicular anisotropy (PA) were prepared by magnetron sputtering with Pt as the buffer layer and the capping layer. The dependence of perpendicular exchange bias (PEB), Hex, on the thickness of the FeMn antiferromagnet (AFM) layer is similar to that of in-plane exchange bias. The value of Hex for the (Pt/Co)3/FeMn multilayer reaches 22.3 kA/m. A thin Pt spacer was inserted between the Co/FeMn interface to enhance PEB. The PEB reaches the largest at 39.8 kA/m when the thickness of the Pt spacer is 0.4 nm.     

银覆盖层对自旋阀三明治结构巨磁电阻的影响

采用射频磁控溅射方法，制备了NiFe/Cu/CoFe和CoFe/Cu/CoFe/NiO两种不同结构类型的自旋阀.当
使用Ag作为镜面覆盖层时，发现当Ag厚度大约在2.0～2.4 nm时，不同结构的自旋阀样品NiFe/Cu/CoFe和
CoFe/Cu/CoFe/NiO的巨磁电阻（GMR）都有较大幅度的提高.对Ag(tAg nm)/NiFe(6 nm)/Cu(2.2 nm)/CoFe
(4 nm)结构自旋阀，当tAg＝2 nm时，样品的GMR达到3.4 ％；对Ag(tAg nm)/CoFe(4 nm)/Cu(2.2 nm)/
CoFe(4 nm)/NiO(70 nm)结构自旋阀，当tAg＝2.4 nm时，样品的GMR从6.9 ％提高到8.3 ％.应用半经典理
论对银覆盖层的镜面反射作用进行了解释.     

Tantalum oxide barrier in magnetic tunnel junctions

Tantalum as an insulating barrier can take the place of A1 in magnetic tunnel junctions (MTJs). Ta barriers in MTJs were fabricated by natural oxidation. X-ray photoelectron spectroscopy (XPS) was used to characterize the oxidation states of Ta barrier.The experimental results show that the chemical state of tantalum is pure Ta5~ and the thickness of the oxide is 1.3 nm. The unoxidized Ta in the barrier may chemically reacted with NiFe layer which is usually used in MTJs to form an intermetallic compound,NiTa2- A magnetic “dead layer“ could be produced in the NiFe/Ta interface. The “dead layer“ is likely to influence the spinning electron transport and the magnetoresistance effect.     

Dependence of domain wall structures on repetition n in[Pt（0.5 nm）/Co（0.4 nm）]n/NiO（1.1 nm）/[Co（0.4 nm）/Pt（0.5 nm）]n multilayers

The magnetic force microscopy and a sample vibrating magnetometer have been used to investigate the domain structure in two antiferromagnetically coupled Co/Pt multilayers.In the antiferromagnetic coupled[Pt(0.5 nm)/Co(0.4 nm)]_n/NiO(1.1 nm)/[Co(0.4 nm)/Pt(0.5 nm)]_n multilayers with perpendicular anisotropy,the antiferromagnetic interlayer coupling strength increases linearly with the repetition number n in Co/Pt multilayers.In demagnetized states,relatively shifted domain walls in the two Co/Pt multila...     

Preparation and properties of 4.25Cu-0.75Ni/NiFe_2O_4 cermet

1INTRODUCTION NiFe2O4cermets,whichareexpectedtobe usedastheinertanodesforaluminumelectrolysis, havelowcorrosionandoxidation,goodelectricalconductivityandhighthermalshockresistance[15]. Nickelferritespinelformsacorrosion resistant networkthatcontainstheelectricallyconductivecopper basedmetallicphase.Especially,Gregget al[6]foundacermetofNiFe2O4 18%NiO 17%Cu (massfraction),whichshowedfavorablecorrosion andconductivitypropertiesasinertanodesinsmalllaboratorycells.However,itwasalsoshowedth…     

Dependence of Magnetic Properties and Microstructure of Ni81Fe19 Film on Base Vacuum and Sputtering Pressure

The Ni81Fe19/Ta films with different NiFe thickness were prepared at different base vacuums and sputtering pressures,The results of magnetic measurement and atomic force microscope(AFM),showed that the films prepared at higher base vacuum and lower sputtering pressure had larger ΔR/R,The reason should be that higher base vacuum and lower sputtering pressure introduce larger grain-size and lower surface roughnes,which will weaken the scattering of electrons,reduce the resistance R,and increase ΔR/R.     

Effect of CaO doping on corrosion resistance of Cu/(NiFe_2O_4-10NiO) cermet inert anode for aluminum electrolysis

The CaO-doped Cu/(NiFe2O4-10NiO) cermet inert anodes were prepared by the cold isostatic pressing-sintering process, and their corrosion resistance to Na3AlF6-K3AlF6-Al2O3 melt was studied. The results show that the relative density of 5Cu/(NiFe2O4-10NiO) cermet sintered at 1 200 ℃ increases from 82.83% to 97.63% when 2% CaO (mass fraction) is added. During the electrolysis, the relative density of cermet inert anode descends owing to the chemical dissolution of additive CaO at ceramic grain boundary, which...     

巨磁电阻效应的非接触光学表征方法研究

根据自平均极限模型推导了在巨磁电阻薄膜中折射系数与自旋非对称因子的关系。用傅立叶变换红外光谱仪组建了磁折射效应测试装置,并测试了自旋阀多层薄膜(Si/PtMn/CoFe/Ru/CoFe/Cu/Co/NiFe)的磁折射效应。结果表明:在红外波段,可以用磁折射效应表征巨磁电阻效应。     

Effects of hydrothermal temperatures on properties of magnetic titanate nanotubes

NiFe2O4 dopeded with magnetic titanate nanotubes(MTNT)were prepared by a hydrothermal method using magnetic nanoparticles TiO2/SiO2/NiFe2O4 as the precursor.The effects of hydrothermal temperatures on their composition,morphologies and magnetic properties of products were characterized by transmission electron microscopy(TEM),scanning electron microscopy(SEM),X-ray diffraction(XRD),vibration sample magnetometer(VSM)and energy dispersive X-ray spectroscopy(EDS).The results show that the hydrothermal temperature has a significant impact on the morphology of the products.The MTNT is synthesized in the temperature range of 120-160 ℃ and the inner diameter of MTNT is about 3-10 nm,the wall thickness 4-12nm and the length 100-200 nm.The components of MTNT are Na0.8H1.2Ti3O7 and a little of anatase TiO2 and NiFe2O4.The ferrimagnetisms and magnetic hysteresis phenomena are shown in the prepared MTNT.The hydrothermal temperature has no clear effect on the magnetic properties in the range of 120-180 ℃.The visible-light photo-catalytic activity of the products decreases as the temperature increases.The decolorization of methylene blue is 94.6% by the MTNT obtained at 120 ℃ and the recovery rate of MTNT is more than 95 percent.The MTNT has excellent photocatalytic activity and is easy to recovery.     

周期换向脉冲电镀参数对Ni—Fe合金镀层成分影响的研究

采用周期换向脉冲电流（ＰＲ）在铁基体上进行了ＮｉＦｅ合金镀的研究。在不改变槽液条件下，改变脉冲参数可获得Ｎｉ／Ｆｅ比不同的合金镀层，以满足使用要求。讨论了脉冲电镀参数对合金镀层成分影响的规律和双脉冲电镀的一些特性。     

Microstructure and AMR Properties of Permalloy Films Sputtered on (Ni_ (0.81)Fe_(0.19)_ (0.66)Cr_(0.34 )Buffer

1　IntroductionTheanisotropicmagnetoresistanceeffect (AMR)waswidelystudiedinthepastyearsbecauseofitspracticalapplicationinmagneticandelectronicdevices ,eg ,themagneticsensorsandreadouthead[1 3 ] .Ni0 .81Fe0 .19hasex cellentmagneticsoftness ,andwasgenerall…     

Ni/BiFeO_3超晶格磁电效应的第一性原理计算

为了探究铁磁/铁电超晶格材料的磁电耦合效应,采用基于密度泛函理论的第一性原理计算方法,研究了Ni/BiFeO_3超晶格的电子结构和磁矩.结果表明,Ni/BiFeO_3超晶格界面处Ni-3d轨道与O-2p轨道发生了强烈的电子杂化作用,Ni和BiFeO_3界面主要通过以O原子为中间媒介的电荷转移进行相互影响.在外加电场作用下,由于铁电极化的存在,超晶格结构上下两个界面存在磁化差异,原子成键和电荷转移重新分布能够引起较强的磁电耦合效应. Ni/BiFeO_3超晶格界面磁电耦合系数约为3. 509×10-~(14)T·cm~2/V.     

ZnFe2O4和NiFe2O4的磁热效应研究

采用水热合成法（180℃）,选择不同pH值和不同反应时间,制备出不同的ZnFe2O4和NiFe2O4磁粉,通过XRD、SEM、VSM图谱对其进行表征分析,并对其在微波磁场中的升温情况进行测量和分析．结果表明,在不同浓度、不同微波功率下,ZnFe2O4流体温度稳定在50．0℃～61．8℃;NiFe2O4流体温度稳定在52．7℃～66．2℃．     

共价反应型多层有机-无机复合膜组装及其渗透汽化性能

对共价反应型多层有机-无机复合膜组装及其渗透汽化性能进行了研究.采用经硅烷偶联剂改性后的管式陶瓷膜作为基膜,通过动态层层吸附自组装(layer-by-layer,LbL)技术在管式陶瓷膜内表面分别组装聚丙烯酸(poly acrylic acid,PAA)/聚乙烯醇(poly vinyl alcohol,PVA)/戊二醛(glutaraldehyde,GA),再通过热交联引发层间反应,生成共价键,形成稳定性较强的多层复合分离膜,并将其用于渗透汽化领域.考察了组装层数、复合时间、交联温度和PVA相对分子质量等条件对复合膜性能的影响.结果表明:当组装层数为5层、进料液温度为75℃时,有机-无机复合膜对95%的乙醇/水体系,其透过液水的质量分数为99.5%,渗透通量可达102 g/(m2·h).     

Magnetic properties and structure of very thin permalloy films

In order to study the magnetic properties and structure of very thin permalloy films, Ni81Fe19 films of 12 nm in thickness were prepared by different instruments at an ultrahigh base vacuum and a lower base vacuum. The anisotropic magnetoresistance coefficients (△R/R) of Ni81Fe19 (12 nm) films reached 1.6 % and 0.6 %, and the coercivities were 127 and 334 A/m, respectively. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to study the structure and surface chemical state. The experimental results show that the films prepared at the ultrahigh base vacuum have a smoother surface, a bigger grain size and a denser structure with fewer defects than those prepared at the lower base vacuum.     

Microstructure and magnetic properties of FePt/MgO multilayers deposited by RF magnetron sputtering

FePt (50 nm) and [FePt(a nm)/MgO(b nm)]5/glass (a=1, 2, 3; b=1, 2, 3) films were prepared by radio frequency (RF) magnetron sputtering technique, and then were annealed at 600°C for 30 min. The effect of MgO layer thickness on the structures and magnetic properties of the FePt/MgO multilayers was investigated. The coercivities and inter-grain interactions of the FePt/MgO films were decreased, yet the degree of (001) texturing drastically increased with the increase in MgO layer thickness when the FePt layer thickness was fixed. Thus, the FePt/MgO films with appropriate coercivities, high perpendicular anisotropy, and weak in-ter-grain interactions were obtained by controlling the MgO layer thickness. Overall, these results indicate that the FePt/MgO nanos-tructured films are promising candidates for future high-density perpendicular recording media.     

Perpendicular magnetic anisotropy of Co85Cr15/Pt multilayers

The CoCr/Pt bilayers and (CoCr/Pt)20 multilayers with Pt underlayer were prepared by DC magnetron sputtering. The effects of prepared condition on perpendicular magnetic anisotropy were investigated. The results show that the thickness of Pt underlayer has a great effect on the microstructure and perpendicular magnetic anisotropy of CoCr/Pt bilayers and (CoCr/Pt)20 multilayers.When the thickness of Pt underlayer increases, Pt(111) and CoCr(002) peaks of both CoCr/Pt bilayers and (CoCr/Pt)20 multilayers increase and the bilayer periodicity of the multilayers is improved. The effective magnetic anisotropy of (CoCr/Pt)20 multilayers with Pt underlayer was much larger than that of CoCr/Pt bilayers. The (CoCr/Pt)20 multilayers has a stronger perpendicular magnetic anisotropy than that of CoCr/Pt bilayers. This is ascribed to the interface magnetic anisotropy of the multilayers.