(Ni0.81Fe0.19)1－xCrx作为种子层对NiFe/PtMn双层膜交换偏置的影响

将NiFe/PtMn双层膜生长在(Ni_0.81Fe_0.19)_1-xCr_x种子层材料上，通过改变种子层中Cr的原子含量，系统的研究了NiFe/PtMn双层膜中PtMn晶粒尺寸和织构对交换偏置的影响.对退火270℃，5h后的NiFe/PtMn双层膜磁性的研究表明,PtMn织构强弱对交换偏置场的影响不明显，而PtMn的晶粒尺寸是影响交换偏置场的主要因素，PtMn颗粒的相干长度在11.3nm左右时得到了较大的交换偏置场. 关键词： NiFe/PtMn双层膜 交换偏置场     

(Ni0.81Fe0.19)1-xCrx作为种子层对NiFe/FeMn交换偏置的影响

采用一种新的种子层材料:(Ni081Fe019)1-xCrx,通过改变种子层中Cr原子的含量,使得在其上生长的NiFeFeMn双层膜的织构和晶粒尺寸产生极大的差异,系统研究了NiFeFeMn双层膜中FeMn晶粒尺寸和织构对交换偏置的影响.实验结果表明,在FeMn的γ相(111)织构较好的前提下,交换偏置场的大小与织构的差异没有关系;FeMn的晶粒尺寸对交换偏置场有很大影响,较小的反铁磁层晶粒对交换偏置场有利,过大的反铁磁层晶粒不利于交换偏置场.将(Ni081Fe019)05Cr05与传统的种子层材料Ta进 关键词： 交换偏置 晶粒尺寸 织构 种子层     

PtMn层厚度对NiFe/PtMn双层膜交换偏置形成及热稳定性的影响

采用磁控溅射的方法制备了一组以(Ni_0.81Fe_0.19)_1-xCr_x作为缓冲层的NiFe/PtMn双层膜样品，研究了NiFe/PtMn双层膜的形成过程和热稳定性.实验表明，Cr成分的不同会引起NiFe/PtMn双层膜中PtMn层晶粒尺寸的不同，使NiFe/PtMn双层膜的交换偏置场与PtMn层厚度之间呈现不同的变化关系.热稳定性实验表明，PtMn晶粒尺寸较大的样品，出现交换偏置现象所需要的临界厚度较小，热稳定性好，这与Mauri的理论模型一致. 关键词： NiFe/PtMn双层膜 交换偏置场 热稳定性     

NiFe/FeMn双层膜的交换耦合

采用平面霍尔效应测量方法，对NiFe/FeMn双层膜的交换耦合进行了研究. 结果表明，在NiFe/FeMn体系中不存在spin-flop模型给出的单轴各向异性场. 而导致交换耦合场可逆与不可逆测量结果之间较大差异的原因是反铁磁颗粒的不稳定性或铁磁层的分畴现象. 关键词： 反铁磁/铁磁双层膜 交换偏置场 可逆与不可逆测量     

NiFe/FeMn双层膜交换偏置的形成及热稳定性研究

研究了在铁磁(NiFe)/反铁磁(FeMn)双层膜之间，交换偏置的形成过程和热稳定性，特别是NiFe/FeMn的交换偏置作用与FeMn层晶粒尺寸的关系.和以前作者不同的是，本文方法采用非磁性Ni-Fe-Cr合金作缓冲层材料，改变Cr的含量就可以获得不同晶粒尺寸的反铁磁FeMn层.实验表明，晶粒尺寸较小的FeMn产生较强的铁磁/反铁磁交换偏置场；但是，对于较大晶粒的FeMn层，出现交换偏置作用所要的临界厚度较小.这符合Mauri提出的理论模型.交换偏置场的热稳定性实验表明，具有较大晶粒尺寸的FeMn层给出较 关键词： 交换偏置 热稳定性 反铁磁 晶粒尺寸     

两步法制备的自旋阀巨磁电阻效应研究

采用新的磁控溅射两步法沉积自旋阀多层膜,不仅交换耦合作用大大增强,而且可以提高磁电阻比值和降低层间耦合作用.得到磁电阻比值～26%,交换耦合场～28kA/m,层间耦合场～01kA/m.自旋阀的下部(缓冲层(Ta)/自由层(NiFe)/中间隔离层(Cu))在低氩气压下沉积、上部(被钉扎层(NiFe)/反铁磁钉扎层(FeMn)/覆盖层(Ta))则在高氩气压下沉积.前者保证了自旋阀具有强(111)晶体织构,平整的NiFe/Cu界面和致密的Cu层,抑制了层间耦合作用;后者则促进小尺寸磁畴生长和增加NiFe/FeM 关键词：     

具有分隔层Bi的反铁磁/铁磁双层薄膜间的短程交换耦合

用磁控溅射方法制备了NiFeⅠFeMnBiNiFeⅡ薄膜,研究了反铁磁薄膜FeMn与铁磁薄膜NiFeⅠ及NiFeⅡ间的交换偏置场Hex相对于分隔层Bi厚度的变化.发现随分隔层Bi厚度的增加,FeMn与NiFeⅠ间的交换偏置场Hex1几乎不变,FeMn与NiFeⅡ间的交换偏置场Hex2急剧减小.当Bi的厚度超过06nm时,FeMn与NiFeⅡ之间的交换偏置场从6925下降为0876kA·m-1.x射线光电子能谱(XPS)分析表明,沉积在FeMnNiFeⅡ界面的Bi并没有全部停留在界面处,至少有部分偏聚到Ni 关键词： 交换偏置 分隔层 织构 XPS     

具有垂直各向异性(Pt/Co)n/FeMn多层膜的交换偏置

采用磁控溅射方法制备了以Pt为缓冲层和保护层的具有垂直各向异性(Pt/Co)_n/ FeMn多层膜.研究结果表明，多层膜的垂直交换偏置场H_ex和反铁磁层厚度的关 系与其具有平面各向异性的交换偏置场随反铁磁层厚度变化趋势相近.随着铁磁层调制周期 数的增加，垂直交换偏置场H_ex相应减小，并且与铁磁层的调制周期数近似成反 比关系.(Pt/Co)₃/FeMn的垂直交换偏置场H_ex已经达到22.3kA/m.为 关键词： 交换偏置 垂直各向异性 多层膜     

具有垂直各向异性(Pt/Co)n/FeMn多层膜的交换偏置

采用磁控溅射方法制备了以Pt为缓冲层和保护层的具有垂直各向异性(Pt/Co)n/FeMn多层膜.研究结果表明,多层膜的垂直交换偏置场Hex和反铁磁层厚度的关系与其具有平面各向异性的交换偏置场随反铁磁层厚度变化趋势相近.随着铁磁层调制周期数的增加,垂直交换偏置场Hex相应减小,并且与铁磁层的调制周期数近似成反比关系.(Pt/Co)3/FeMn的垂直交换偏置场Hex已经达到22.3kA/m.为了进一步提高Hex,在Co/FeMn的界面插入Pt层,当Pt层厚度为0.4nm时,Hex达到最大值39.8kA/m.     

分子束外延生长Fe/Fe50Mn50双层膜的交换偏置

利用表面磁光克尔效应和铁磁共振对分子束外延生长的Fe/Fe₅₀Mn₅₀双层膜的交换偏置场和矫顽力进行了研究,实验结果表明,当反铁磁层厚度小于55nm时 ,不出现交换偏置,而当大于这一厚度时,出现交换偏置;大约在7nm时,达到极大值.随着 反铁磁层厚度的继续增大,偏置场和矫顽力随Fe₅₀Mn₅₀膜厚的增大 而下降.铁磁共振实验结果表明样品的磁性存在单向各向异性.并对上述结果进行了讨论. 关键词： 分子束外延 50Mn₅₀')" href="#">Fe/Fe₅₀Mn₅₀ 双层膜 交换偏置     

Bi对自旋阀钉扎场的影响及机理

实验发现将Bi插入自旋阀多层膜TaNiFeCuBi(x)NiFeFeMn中可以显著地提高自旋阀的钉扎场Hex.采用XPS对Cu,Bi元素的分布情况进行了研究,发现Bi的插入明显抑制了Cu原子在自旋阀的制备过程中在NiFeFeMn界面的偏聚.进一步研究表明:自旋阀钉扎层NiFeFeMn界面中,Cu原子的存在是导致自旋阀Hex小于TaNiFeFeMn多层膜Hex的主要原因. 关键词： 自旋阀 钉扎场 交换各向异性 表面活化剂     

Suppression of interlayer segregation in spin-valve NiFe/Cu/NiFe/FeMn multilayers

Experimental results show that Cu atoms can float out to or segregate to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta spin-valve multilayers, which results in a drop of the exchange-coupling field (H_ex) of NiFe/FeMn in the spin-valve multilayers. However, when a small amount of Bi atoms is deposited between the Cu and the pinned NiFe layers, Cu segregation to the NiFe/FeMn interface can be suppressed. At the same time, H_ex of NiFe/FeMn in the spin-valve multilayers with a Bi interfacial layer can be effectively increased. PACS 75.70.Cn; 82.80.Pv     

Magnetoresistance and magnetization studies through a Cu interlayer in spin valves of NiFe/Cu/NiFe/FeMn

The influence of the Cu layer thickness on the magnetic and magnetotransport properties has been investigated in Ta/NiFe/Cu/NiFe/FeMn spin valves. The magnetization and magnetoresistance measurements were carried out for magnetic field applied along the easy-axis direction. A phenomenological model, which assumes formation of a planar domain wall at the anti-ferromagnetic side of the interfaces as well as bilinear coupling between the ferromagnetic layers, was used to derive the anisotropy characteristics and orientation of each NiFe layer magnetization. The anisotropy and spin valve magnetoresistance were simulated numerically and compared with the experiment. It was found that the anisotropy magnetoresistance is negligible and that there is a poor agreement for the spin-valve one, which was attributed to the model (valid for ferromagnetic layers in single-domain state only) used for its calculation. It was found that the increase of the Cu layer thickness provokes a decrease of the interdiffusion between the NiFe and FeMn layers, and, as consequence, changes of the uniaxial anisotropy of the pinned NiFe layer, of the exchange interaction between the pinned NiFe layer and the FeMn ones, as well as of the exchange-bias field of the pinned NiFe layer.     

Huge exchange-coupling field observed in FeMn-pinned spin valve with ultra-thin pinned NiFe layer

A conventional Ta/NiFe/Cu/NiFe/FeMn/Ta spin valve multilayer was prepared to investigate the exchange bias variations of the pinned NiFe layer. An exchange bias field of 560 Oe has been found in a valve multilayer with ultra-thin pinned NiFe layers (1 nm), in which a large constant magnetic field of 700 Oe was applied during film deposition procession. The observed results are attributed to the large applied magnetic field, which produced more net spins of the antiferromagnet at the interface. These interfacial uncompensated spins provide the net spin moments required for exchange coupling and bias.     

Improving exchange-coupling field in the same thickness of pinned magnetic layer

A conventional Ta/NiFe/Cu/NiFe/FeMn spin valve was prepared to investigate the exchange bias properties with the variations of deposition field. By enhancing the deposition magnetic fields from 50 to 650 Oe, increase of exchange bias fields at a given thickness of the pinned NiFe layer has been found in the spin valves. In this paper, we show that this increase is due to the change of magnetic moment distribution at the ferromagnetic and antiferromagnetic interface by comparison of measured results with the interfacial uncompensated model. Therefore, by enhancing deposition magnetic fields, a large exchange-coupling field can be achieved in relatively thicker magnetic films for application.     

几种元素的界面插层对Ta/NiFe/Ta的各向异性磁电阻效应的影响

文章中,通过磁控溅射制备了界面处插入4d,5d元素薄层(包括Ru,Pd,Ag和Au)的Ta/NiFe/Ta多层膜,并对它们的磁输运和磁性以及微结构进行了测试和表征.结果显示,Pd和Pt一样界面效应显著,能有效地提高NiFe薄膜退火前后的AMR比值,并抑制磁性死层.表面能比较小、熔点相对低的插层材料Ag,Au在退火过程中容易通过晶界扩散,强烈破坏其AMR性能.对于熔点高、表面能比较大的插层材料如Ru,磁性死层同样得到了抑制,NiFe薄膜的温度稳定性也可以得到提高.结果表明界面插层从界面电子自旋-轨道散射、界面死层和界面原子扩散等方面深刻影响NiFe薄膜的AMR. 关键词： 各向异性磁电阻 界面效应 原子扩散     

Effect of Ta buffer and NiFe seed layers on pulsed-DC magnetron sputtered Ir20Mn80/Co90Fe10 exchange bias

A systematic investigation has been done on the correlation between texture, grain size evolution and magnetic properties in Ta/Ni₈₁Fe₁₉/Ir₂₀Mn₈₀/Co₉₀Fe₁₀/Ta exchange bias in dependence of Ta buffer and NiFe seed layer thickness in the range of 2-10 nm, deposited by pulsed DC magnetron sputtering technique. A strong dependence of 〈1 1 1〉 texture on the Ta/NiFe thicknesses was found, where the reducing and increasing texture was correlated with exchange bias field and unidirectional anisotropy energy constant at both NiFe/IrMn and IrMn/CoFe interfaces. However, a direct correlation between average grain size in IrMn and H_ex and H_c was not observed. L1₂ phase IrMn₃ could be formed by thickness optimization of Ta/NiFe layers by deposition at room temperature, for which the maximum exchange coupling parameters were achieved. We conclude finally that the coercivity is mainly influenced by texture induced interfacial effects at NiFe/IrMn/CoFe interfaces developing with Ta/NiFe thicknesses.     

Exchange bias studies of NiFe/FeMn/NiFe trilayer by ion beam etching

Effect of low energy ion beam etching on exchange bias in NiFe/FeMn/NiFe trilayer is investigated in multilayers prepared by rf magnetron sputtering. Stepwise etching and magnetization measurement of FeMn layer in an NiFe/FeMn bilayer show increase of bias as etching proceeds and FeMn thickness decreases. The bias show a maximum around 7 nm FeMn thickness and then fall sharply below 5 nm, broadly in line with the exchange bias variation at increasing FeMn thickness but in reverse order, particularly at low FeMn thickness. Progressive etching of top NiFe layer in the NiFe/FeMn/NiFe trilayer shows an initial gradual increase in bias followed by a sharp increase below 7 nm thickness of top NiFe layer, with a maximum at 2 nm thickness for both NiFe layers and greater bias for seed NiFe layer.     

Interface reaction of Ta/NiO and its effect on exchange coupling

Ta/NiO/NiFe/Ta multilayers, utilizing Ta as the buffer layer, were prepared by RF reactive and DC magnetron sputtering. The exchange coupling field between NiO and NiFe reached a maximum value of 120 Oe at a NiO film thickness of 50 nm. The composition and chemical state at the interface region of Ta/NiO/Ta were studied using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that there is an `intermixing layer’ at the Ta/NiO (and NiO/Ta) interface due to a thermodynamically favorable reaction: 2Ta+5NiO=5Ni+Ta<sub>2</sub>O<sub>5</sub>. This interface reaction has an effect on the exchange coupling. The thickness of the `intermixing layer’ as estimated by XPS depth-profiles was about 8–10 nm.