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…     

Magnetic property and interlayer segregation in spin valve metal multilayers

The experimental results show that the exchange coupling field of NiFe/FeMn for Ta/ NiFe/FeMn/Ta multilayers is higher than that for the spin valve multilayers Ta/NiFe/Cu/NiFe/FeMn/ Ta. In order to find out the reason, the composition and chemical states at the surfaces of Ta( 12nm)/ NiFe(7nm), Ta( 12nm)/NiFe(7nm)/Cu(4nm) and Ta( 12nm)/NiFe(7nm)/Cu(3nm)/NiFe(5nm) were studied using the X-ray photoelectron spectroscopy (XPS). The results show that no elements from lower layers float out or segregate to the surface for the first and second samples. However, Cu atoms segregate to the surface of Ta(12nm)/NiFe(7nm)/Cu(3nm)/NiFe(5nm) multilayers, i.e. Cu atoms segregate to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers. We believe that the presence of Cu atoms at the interface of NiFe/FeMn is one of the important factors causing the exchange coupling field of Ta/NiFe/FeMn/Ta multilayers to be higher than that of Ta/NiFe/Cu/NiFe/ FeMn/Ta multilayers.     

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     

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…     

Observation of Magnetic Domain Structures of Magnetic Thin Films by the Lorentz Electron Microscopy

Inthisdecade,agreatmanyresearchworksonmulti-layeredmopeticthinfilmshavebeenreport6d,sincethemagneticmulti-layeredfilmsarethemosthopefulnovelmagneticmaterialsforthenextgenerationelectionicdevises,suchasgialmagneto-resiSbocesensorelemeds.hiordertOdevel...     

Microstructure and AMR Properties of Permalloy Films Sputtered on （Ni0.81Fe0. 19 ）0.66Cr0.34 Buffer

(Ni_0.81 Fe_0.19)_0.66 Cr_0.34 has a high resistivity and a crystal structure close to that of Ni_0.81 Fe_0.19. The electrical and X-ray diffraction measurements prove that a thin NiFeCr seed layer induces a well (111)-orented Ni_0.81 Fe_0.19 film. Post-annealing treatment improves the magnetic properties of (Ni_0.81Fe_0.19)_0.66 Cr_0.34(45Å)/Ni_0.81Fe_0.19 (150Å)/Ta(55Å) thin film prepared under a deposition field, whereas the inter-diffusion of NiFe/Ta deteriorates the magnetoresistance properties of the film.     

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.     

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℃．     

XPS Studies of Magnetic Multilayers

NiOx/N81Fe19 and Co/AlOx/Co magnetic multilayers were fabricated by reactive RF/DC magnetron sputtering on clean glass substrates and oxidized Si (100) substrates, respectively. The exchange biasing field (Hex) between NiOx, and Ni81Fe19 as a function of NiOx, oxidation states was studied by X-ray photoelectron spectroscopy (XPS). The oxidation states and the oxide thickness of Al layers in magnetic multilayer films consisting of Co/AlOx/Co were also analyzed. It is found that the Hex of NiOx/Ni81Fe19 films only depends on Ni2+ but not on Ni3+ or Ni. The bottom Co can be completely covered by depositing an Al layer thicker than 2.0 nm. The oxide layer was Al2O3, and its thickness was 1.15 nm.     

Al-Al2O3-铁磁金属隧道结界面的表征

用梯形势垒模型计算偏置Al Al2 O3 铁磁金属 (Fe ,Co ,Ni和Ni80 Fe2 0 )隧道结的I V曲线 ,通过与结在 77K温度下的实验I V曲线拟合决定了结的势垒参数 .拟合结果表明 ,对于上电极为不同铁磁金属的 4种结 ,Al Al2 O3 界面处的势垒高度差别很小 ,而Al2 O3 Fe ( Co , Ni, Ni80 Fe2 0 )界面处的势垒高度以及势垒宽度则分别为 1 72eV ,1 76eV ,1 86eV ,1 6 9eV以及 1 7 6 0 ,1 1 2 2 ,1 2 2 8 ,1 3 4 0 .势垒高度和宽度因铁磁金属上电极不同而改变的现象可归因为铁磁金属原子向Al2 O3 势垒层渗透 ,以及在界面区域铁磁金属原子与Al2 O3 的氧化反应导致附加氧化势垒层的形成 .     

微型磁通门工艺的研究

为了制备体积小重量轻的可用于航天方面的微型磁传感器,用微机械加工方法制备了微型磁通门芯片.重点研究用蒸镀和掩膜电铸两种途径制备微型磁通门磁芯的工艺,研究了不同电铸工艺参数(镀液中c(Fe~(2+))/c(Ni~(2+))比、电流密度、pH 值)对镀层组份的影响并获得较为理想的成分比.利用振动样品磁强计测得磁芯材料的磁滞回线表明电镀的磁芯性能优于蒸镀的.     

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.     

微型磁通门工艺的研究

为了制备体积小重量轻的可用于航天方面的微型磁传感器，用微机械加工方法制备了微型磁通门芯片。重点研究用蒸镀和掩膜电铸两种途径制备微型磁门磁芯的工艺，研究了不同电铸工艺参数（镀液中cFe^2 ）／c（Ni^2＋）比、电流密度、pH值）对镀层组份的影响并获得较为理想的成分比。利用振动样品磁强计测得磁芯材料的磁滞回线表明电镀的磁芯性能优于蒸镀的。     

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.     

磁性隧道结隧穿电导和磁电阻的研究

针对由一平面磁性势垒隔开的两铁磁性金属电极构成的磁性隧道结,基于自由电子近似并利用传递矩阵方法计算了其零偏压下的隧穿电导、自旋极化率和隧穿磁阻比率,研究表明隧道结的磁结构对TC(隧穿电导)和TMR(隧穿磁阻)的值有很大的影响,当两磁性电极分子场方向相同,且都与势垒层分子场反平行时,TC数值达到最大,两者平行时,TC的数值最小,同时还分析了分子场的相对取向等对磁性隧道结自旋极化电子输运性质的影响。研究结果对自旋电子器件的设计具有一定的指导意义。     

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。     

Mechanistic investigation into the role of aluminum diffusion in the oxidation behavior of cryomilled NiCrAlY bond coat

High temperature oxidation behavior of the bond coat layer is a critical factor that controls the failure mechanism of thermal barrier coatings (TBCs). Previous work reveald that TBCs with cryomilled NiCrAlY bond coats exhibited an improved oxidation behavior compared to equivalent TBCs with conventional bond coats. The cryomilled NiCrAlY bond coats contributed to a slower growth rate of thermally grown oxides (TGO) with a final thinner thickness and enhanced homogeneity in TGO composition. To better understand the improved oxidation behavior, a mechanistic investigation based on diffusion theory and quantum mechanics is performed to elucidate the role of aluminum diffusion in the oxidation behavior and how the microstructural features of the cryomilled NiCrAlY bond coats, i e, the creation of a thermally stable, uniform distribution of ultrafine Al-rich oxide dispersoids, affect the diffusion kinetics of Al and the migration of free electrons. It is revealed that these Al-rich oxide dispersoids result in a uniform diffusion of Al and slow migration of free electrons within the NiCrAlY bond coat, consequently leading to the improved oxidation behavior.     

Effect of Auxiliary Gas Flow Parameters on Microstructure and Properties of Ta Coatings Prepared by Three-Cathode Atmosphere Plasma Spraying

Based on the three-cathode plasma spraying system, tantalum (Ta) coatings were prepared on the substrate of CuCrZr alloy. The effects of different auxiliary gas (helium) flow rates on the microstructure, phase composition, mechanical and wear resistance properties of Ta coatings were studied. The results showed that the oxidation degree of the coatings decreases first and then increases with the increase of the auxiliary gas flow. When the auxiliary gas flow rate is 70 L·min–1, the oxidation degree of the coating is the lowest, minimum value of the porosity is 0.21%, and the bonding strength reaches the maximum, 59.3 MPa. At this time, the coating wear rate is 0.0012 mm3·N–1·m–1 with the best wear resistance. This indicates that the auxiliary gas flow has an important influence on the quality and surface mechanical properties of tantalum coating.     

载流子平衡的低压高效有机白光器件

研究了结构为ITO/m-MTDATA:x%4F-TCNQ/NPB/TBADN:EBDP:DCJTB/Bphen:Liq/LiF/Al的有机白光电致发光器件(WOLED)。分别在ITO与NPB间加入高迁移率的m-MTDATA:4F-TCNQ来增强器件的空穴注入,在阴极和发光层间加入高迁移率的Bphen:Liq层增强器件的电子注入,降低驱动电压,提高器件效率。同时,由于注入的电子和空穴数量偏离平衡,器件的效率也会受到影响。实验中,通过调节4F-TCNQ的掺杂浓度来调控空穴的注入和传输,使载流子达到高度平衡。器件的最大电流效率和流明效率分别达到了9.3cd/A和4.6 lm/W。     

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。