The principle of planc-to-plane perpendicularity measuring with coordinate measuring machine (CMM) is described and the main factors that influence the measuring precision are analyzed. The minimum condition method ...The principle of planc-to-plane perpendicularity measuring with coordinate measuring machine (CMM) is described and the main factors that influence the measuring precision are analyzed. The minimum condition method is adopted to eliminate the fitting error of the datum plane. In order to diminish the length error of the object plane, the tactics of measuring some part of the plane and then scale to the whole plane is employed. With large quantity of measuring experiments on fiat plates, the most appropriate number of points in measuring a plane is determined to reduce the sampling error.展开更多
Depth estimation is an important task in computer vision.Collecting data at scale for monocular depth estimation is challenging,as this task requires simultaneously capturing RGB images and depth information.Therefore...Depth estimation is an important task in computer vision.Collecting data at scale for monocular depth estimation is challenging,as this task requires simultaneously capturing RGB images and depth information.Therefore,data augmentation is crucial for this task.Existing data augmentationmethods often employ pixel-wise transformations,whichmay inadvertently disrupt edge features.In this paper,we propose a data augmentationmethod formonocular depth estimation,which we refer to as the Perpendicular-Cutdepth method.This method involves cutting realworld depth maps along perpendicular directions and pasting them onto input images,thereby diversifying the data without compromising edge features.To validate the effectiveness of the algorithm,we compared it with existing convolutional neural network(CNN)against the current mainstream data augmentation algorithms.Additionally,to verify the algorithm’s applicability to Transformer networks,we designed an encoder-decoder network structure based on Transformer to assess the generalization of our proposed algorithm.Experimental results demonstrate that,in the field of monocular depth estimation,our proposed method,Perpendicular-Cutdepth,outperforms traditional data augmentationmethods.On the indoor dataset NYU,our method increases accuracy from0.900 to 0.907 and reduces the error rate from0.357 to 0.351.On the outdoor dataset KITTI,our method improves accuracy from 0.9638 to 0.9642 and decreases the error rate from 0.060 to 0.0598.展开更多
[FePt/Ag]n multilayers were deposited on glass substrates by RF magnetron sputtering and ex situ annealed at 550℃ for 30 min. The effects of inserted Ag layer thickness and the number of bilayer repetitions (n) on ...[FePt/Ag]n multilayers were deposited on glass substrates by RF magnetron sputtering and ex situ annealed at 550℃ for 30 min. The effects of inserted Ag layer thickness and the number of bilayer repetitions (n) on the structure and magnetic properties of the multilayers were investigated. It was found that the difference between in-plane and out-of-plane coercivities varied with an increase of inserted Ag layer thickness in the [FePt 2 nm/Ag x nm]10 multilayers. The ratio of out-of-plane coercivity to in-plane coercivity reached the maximum value with the Ag layer thickness of 5 nm, indicating that the Ag layer thickness plays an important role in obtaining perpendicular orientation. For the [FePt 2 nm/Ag 5 um]n multilayers, perpendicular orientation is also influenced by n. The maximum value of the ratio of out-of-plane coercivity to in-plane coercivity appeared when n was given as 8. It was found that the [FePt 2 nm/Ag 5 nm]8 had a high perpendicular coercivity of 520 kA/m and a low in-plane one of 88 kA/m, which shows a strong perpendicular anisotropy.展开更多
Graphene-based materials on wearable electronics and bendable displays have received considerable attention for the mechanical flexibility,superior electrical conductivity,and high surface area,which are proved to be ...Graphene-based materials on wearable electronics and bendable displays have received considerable attention for the mechanical flexibility,superior electrical conductivity,and high surface area,which are proved to be one of the most promising candidates of stretching and wearable sensors.However,polarized electric charges need to overcome the barrier of graphene sheets to cross over flakes to penetrate into the electrode,as the graphene planes are usually parallel to the electrode surface.By introducing electron-induced perpendicular graphene(EIPG)electrodes incorporated with a stretchable dielectric layer,a flexible and stretchable touch sensor with"in-sheet-chargestransportation"is developed to lower the resistance of carrier movement.The electrode was fabricated with porous nanostructured architecture design to enable wider variety of dielectric constants of only 50-μm-thick Ecoflex layer,leading to fast response time of only 66 ms,as well as high sensitivities of 0.13 kPa-1 below 0.1 kPa and 4.41 MPa-1 above 10 kPa,respectively.Moreover,the capacitance-decrease phenomenon of capacitive sensor is explored to exhibit an object recognition function in one pixel without any other integrated sensor.This not only suggests promising applications of the EIPG electrode in flexible touch sensors but also provides a strategy for internet of things security functions.展开更多
In a magnetic nanostripe, the effects of perpendicular magnetic anisotropy(PMA) on the current-driven horizontal motion of vortex wall along the stripe and the vertical motion of the vortex core are studied by micro...In a magnetic nanostripe, the effects of perpendicular magnetic anisotropy(PMA) on the current-driven horizontal motion of vortex wall along the stripe and the vertical motion of the vortex core are studied by micromagnetic simulations.The results show that the horizontal and vertical motion can generally be monotonously enhanced by PMA. However, when the current is small, a nonmonotonic phenomenon for the horizontal motion is found. Namely, the velocity of the horizontal motion firstly decreases and then increases with the increase of the PMA. We find that the reason for this is that the PMA can firstly increase and then decrease the confining force induced by the confining potential energy. In addition, the PMA always enhances the driving force induced by the current.展开更多
Microstructures and magnetic properties of Ta/Pt/Co 2 FeAl(CFA)/MgO multilayers are studied to understand perpendicular magnetic anisotropy(PMA) of half-metallic full-Heusler alloy films.PMA is realized in a 2.5-n...Microstructures and magnetic properties of Ta/Pt/Co 2 FeAl(CFA)/MgO multilayers are studied to understand perpendicular magnetic anisotropy(PMA) of half-metallic full-Heusler alloy films.PMA is realized in a 2.5-nm CFA film with B2-ordered structure observed by a high resolution transmission electron microscope.It is demonstrated that a high quality interface between the ferromagnetic layer and oxide layer is not essential for PMA.The conversions between in-plane anisotropy and PMA are investigated to study the dependence of magnetic moment on temperature.At the intersection points,the decreasing slope of the saturation magnetization(M s) changes because of the conversions.The dependence of M s on the annealing temperature and MgO thickness is also studied.展开更多
Recent progresses in magnetic tunnel junctions with perpendicular magnetic anisotropy (PMA) are reviewed and summarized. At first, the concept and source of perpendicular magnetic anisotropy (PMA) are introduced. ...Recent progresses in magnetic tunnel junctions with perpendicular magnetic anisotropy (PMA) are reviewed and summarized. At first, the concept and source of perpendicular magnetic anisotropy (PMA) are introduced. Next, a historical overview of PMA materials as magnetic electrodes, such as the RE-TM alloys TbFeCo and GdFeCo, novel tetragonal manganese alloys Mn-Ga, L10-ordered (Co, Fe)/Pt alloy, multilayer film [Co, Fe, CoFe/Pt, Pd, Ni, AU]N, and ultra-thin magnetic metal/oxidized barrier is offered. The other part of the article focuses on the optimization and fabrication of CoFeB/MgO/CoFeB p-MTJs, which is thought to have high potential to meet the main demands for non-volatile magnetic random access memory.展开更多
ZSM-5 plates with a perpendicular intergrowth structure was synthesized by using a simple amine as the structure directing agent under hydrothermal conditions,in which the mother plate and the perpendicularly standing...ZSM-5 plates with a perpendicular intergrowth structure was synthesized by using a simple amine as the structure directing agent under hydrothermal conditions,in which the mother plate and the perpendicularly standing plates oriented along the(010)and(100)planes of MFI crystals,respectively.During the crystallization process,the mother plate was initially formed on the surface of the amorphous solid gel,while a set of parallel plates perpendicularly grew on its surface,via a homogeneous nucleation mechanism.The mother plate and the perpendicular plates had a similar thickness of 100-200 nm and were characterized by considerably shortened straight and zigzag 10 member ring pores,respectively.This unique intergrowth structure greatly facilitated the diffusion of the reactive molecules in HZSM-5 crystals during methanol conversion to hydrocarbons.展开更多
The present work is concerned with the problem of mode Ⅲ crack perpendicular to the interface of a bi-strip composite. One of these strips is made of a functionally graded material and the other of an isotropic mater...The present work is concerned with the problem of mode Ⅲ crack perpendicular to the interface of a bi-strip composite. One of these strips is made of a functionally graded material and the other of an isotropic material, which contains an edge crack perpendicular to and terminating at the interface. Fourier transforms and asymptotic analysis are employed to reduce the problem to a singular integral equation which is numerically solved using Gauss-Chebyshev quadrature formulae. Furthermore, a parametric study is carried out to investigate the effects of elastic and geometric characteristics of the composite on the values of stress intensity factor.展开更多
Off-stoichiometric full-Heusler alloy Co_2 MnAl thin films with different thicknesses are epitaxially grown on GaAs(001) substrates by molecular-beam epitaxy. The composition of the films, close to Co_(1.65)Mn_(1.35)A...Off-stoichiometric full-Heusler alloy Co_2 MnAl thin films with different thicknesses are epitaxially grown on GaAs(001) substrates by molecular-beam epitaxy. The composition of the films, close to Co_(1.65)Mn_(1.35)Al(CMA),is determined by x-ray photoelectron spectroscopy and energy dispersive spectroscopy. Tunable perpendicular magnetic anisotropy(PMA) from 3.41 Merg/cm^3 to 1.88 Merg/cm^3 with the thickness increasing from 10 nm to 30 nm is found,attributed to the relaxation of residual compressive strain. Moreover, comparing with the ultrathin CoFeB/MgO used in the conventional perpendicular magnetic tunnel junction, the CMA electrode has a higher magnetic thermal stability with more volume involved. The PMA in CMA films is sustainable up to 300℃,compatible with semiconductor techniques. This work provides a possibility for the development of perpendicular magnetized full-Heusler compounds with high thermal stability and spin polarization.展开更多
We demonstrate that radio frequency(RF)magnetron sputtering technique can modify the perpendicular magnetic anisotropy(PMA)of Pt/Co/normal metal(NM)thin films.Influence of ion irradiation during RF magnetron sputterin...We demonstrate that radio frequency(RF)magnetron sputtering technique can modify the perpendicular magnetic anisotropy(PMA)of Pt/Co/normal metal(NM)thin films.Influence of ion irradiation during RF magnetron sputtering should not be neglected and it can weaken PMA of the deposited magnetic films.The magnitude of this influence can be controlled by tuning RF magnetron sputtering deposition conditions and the upper NM layer thickness.According to the stopping and range of ions in matter(SRIM)simulation results,defects such as displacement atoms and vacancies in the deposited film will increase after the RF magnetron sputtering,which can account for the weakness of PMA.The amplitude changes of the Hall resistance and the threshold current intensity of spin orbit torque(SOT)induced magnetization switching also can be modified.Our study could be useful for controlling magnetic properties of PMA films and designing new type of SOT-based spintronic devices.展开更多
Spin-orbit torque(SOT)has been considered as one of the promising technologies for the next-generation magnetic random access memory(MRAM).So far,SOT has been widely utilized for inducing various modes of magnetizatio...Spin-orbit torque(SOT)has been considered as one of the promising technologies for the next-generation magnetic random access memory(MRAM).So far,SOT has been widely utilized for inducing various modes of magnetization switching.However,it is a challenge that so many multiple modes of magnetization switching are integrated together.Here we propose a method of implementing both unipolar switching and bipolar switching of the perpendicular magnetization within a single SOT device.The mode of switching can be easily changed by tuning the amplitude of the applied current.We show that the field-like torque plays an important role in switching process.The field-like torque induces the precession of the magnetization in the case of unipolar switching,however,the field-like torque helps to generate an effective zcomponent torque in the case of bipolar switching.In addition,the influence of key parameters on the mode of switching is discussed,including the field-like torque strength,the bias field,and the current density.Our proposal can be used to design novel reconfigurable logic circuits in the near future.展开更多
A 3-dimensional(3D)micromagnetic model combined with Fast Fourier Transform(FFT)method was built up to study the writability in the L1_(0)FePt perpendicular medium.The effects of controllable grain size distributions ...A 3-dimensional(3D)micromagnetic model combined with Fast Fourier Transform(FFT)method was built up to study the writability in the L1_(0)FePt perpendicular medium.The effects of controllable grain size distributions were studied by grain growth simulation.It is found that the cross-track-averaged magnetization changes little between the L1_(0)FePt medium with uniform or non-uniform grain size distribution.展开更多
The single-pole tip (SPT) heads made of the high saturation FeCo ferromagnetic metals are crucial for the actualization of ultrahigh density perpendicular recording. The effective head field distribution in the medium...The single-pole tip (SPT) heads made of the high saturation FeCo ferromagnetic metals are crucial for the actualization of ultrahigh density perpendicular recording. The effective head field distribution in the medium is of key importance for the design of the SPT head, which would be analyzed by micromagnetic simulations in this work. Two 3D micromagnetic models of the SPT head were established to select a more appropriate method of modeling, with a magnetostatic image effect or a real soft magnetic material to model the image of the SPT head in soft under layer (SUL). The results from these two designs were tested and compared to the ideal head field calculated by the Jacobi finite element method (FEM); and the design with the real soft magnetic material as image was proved suitable for simulating the ultrahigh density perpendicular recording write head.展开更多
(FePt/Ag)n nano-multilayers were deposited on MgO (100) single crystal with laser ablation and then subjected to annealing. FePt L1o grains with (001) texture and thus a large perpendicular magnetic anisotropy constan...(FePt/Ag)n nano-multilayers were deposited on MgO (100) single crystal with laser ablation and then subjected to annealing. FePt L1o grains with (001) texture and thus a large perpendicular magnetic anisotropy constant Ku of the order of 106 J/m3 were formed. A thick Ag layer is found to be favorable for decreasing the dispersion of the easy axis for magnetization. The measurement of time decay of magnetization gave rise to a small activation volume of the order of 10-25m3, showing the promising of being the recording medium for future high density perpendicular recording.展开更多
(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 ...(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 anfiferromagnet (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.展开更多
Co2FeA10.5Si0.5 (CFAS)-based multilayers sandwiched by MgO layers have been deposited and annealed at different temperatures. Perpendicular magnetic anisotropy (PMA) with the magnetic anisotropy energy density Ku ...Co2FeA10.5Si0.5 (CFAS)-based multilayers sandwiched by MgO layers have been deposited and annealed at different temperatures. Perpendicular magnetic anisotropy (PMA) with the magnetic anisotropy energy density Ku ≈2.5x106 erg/cm3 (1 erg = 10-7 J) and the coercivity He = 363 Oe (10e = 79.9775 A.m-1) has been achieved in the Si/SiO2/MgO (1.5 nm)/CFAS (2.5 nm)/MgO (0.8 nm)/Pt (5 nm) film annealed at 300 ℃. The strong PMA is mainly due to the top MgO layer. The structure can be used as top magnetic electrodes in half-metallic perpendicular magnetic tunnel junctions.展开更多
The structures of water inside and outside (6,6), (8,8), and (10,10) single- walled carbon nanotubes (SWCNTs) under an electric field perpendicular to the tube axis are investigated by molecular dynamics simul...The structures of water inside and outside (6,6), (8,8), and (10,10) single- walled carbon nanotubes (SWCNTs) under an electric field perpendicular to the tube axis are investigated by molecular dynamics simulations. The results show that dipole reorientation induced by electric field plays a significant role on the structures of confined water inside and outside SWCNTs. Inside SWCNTs, the average water occupancy and the average number of hydrogen bonds (H-bonds) per water molecule decrease as the electric intensity increases. Because the field intensity is sufficiently strong, the initial water structures inside the SWCNTs are destroyed, and the isolated water clusters are found. Outside SWCNTs, the azimuthal distributions of the density and the average number of H-bonds per water molecule around the solid walls become more and more asymmetric as the electric intensity increases. The percentages of water molecules involved in 0-5 H-bonds for all the three types of SWCNTs under different field intensities are displayed. The results show that those water molecules involved with most H-bonds are the most important to hold the original structures. When the electric field direction is parallel with the original preferred orientation, the density and the H-bond connections in water will be increased; when the electric field direction is perpendicular to the original preferred orientation, the density and the H-bond connections in water will be decreased.展开更多
In this article, we review the recent progress in growth, structural characterizations, magnetic properties, and related spintronic devices of tetragonal MnxGa and MnxA1 thin films with perpendicular magnetic anisotro...In this article, we review the recent progress in growth, structural characterizations, magnetic properties, and related spintronic devices of tetragonal MnxGa and MnxA1 thin films with perpendicular magnetic anisotropy. First, we present a brief introduction to the demands for perpendicularly magnetized materials in spintronics, magnetic recording, and perma- nent magnets applications, and the most promising candidates of tetragonal MnxGa and MnxA1 with strong perpendicular magnetic anisotropy. Then, we focus on the recent progress of perpendicularly magnetized MnxGa and MnxA1 respec- tively, including their lattice structures, bulk synthesis, epitaxial growth, structural characterizations, magnetic and other spin-dependent properties, and spintronic devices like magnetic tunneling junctions, spin valves, and spin injectors into semiconductors. Finally, we give a summary and a perspective of these perpendicularly magnetized Mn-based binary alloy films for future applications.展开更多
The exchange-coupled [Co/Ni]N/Tb Fe nano-magnetic films can display strong perpendicular magnetic anisotropy(PMA) which depends on the Tb:Fe component ratio, Tb Fe layer thickness and the repetition number N of [Co/Ni...The exchange-coupled [Co/Ni]N/Tb Fe nano-magnetic films can display strong perpendicular magnetic anisotropy(PMA) which depends on the Tb:Fe component ratio, Tb Fe layer thickness and the repetition number N of [Co/Ni]Nmultilayer. Perpendicular spin valves in the nano thickness scale, consisting of a [Co/Ni]3free and a [Co/Ni]5/Tb Fe reference multilayer, show high giant magnetoresistance(GMR) signal of 6.5 % and a large switching field difference over3 k Oe. However, unexpected slanting of the free layer magnetization, accompanied by a reduced GMR ratio, was found to be caused by the presence of a thick Fe-rich or even a thin but Tb-rich Tb Fe layer. We attribute this phenomenon to the large magnetostriction effect of Tb Fe which probably induces strong stress acting on the free layer and hence reduces its interfacial PMA.展开更多
基金sponsored by the Special Research Fund for Young Teachers of Universities in Shanghai under Grant No.gjd-07048
文摘The principle of planc-to-plane perpendicularity measuring with coordinate measuring machine (CMM) is described and the main factors that influence the measuring precision are analyzed. The minimum condition method is adopted to eliminate the fitting error of the datum plane. In order to diminish the length error of the object plane, the tactics of measuring some part of the plane and then scale to the whole plane is employed. With large quantity of measuring experiments on fiat plates, the most appropriate number of points in measuring a plane is determined to reduce the sampling error.
基金the Grant of Program for Scientific ResearchInnovation Team in Colleges and Universities of Anhui Province(2022AH010095)The Grant ofScientific Research and Talent Development Foundation of the Hefei University(No.21-22RC15)+2 种基金The Key Research Plan of Anhui Province(No.2022k07020011)The Grant of Anhui Provincial940 CMC,2024,vol.79,no.1Natural Science Foundation,No.2308085MF213The Open Fund of Information Materials andIntelligent Sensing Laboratory of Anhui Province IMIS202205,as well as the AI General ComputingPlatform of Hefei University.
文摘Depth estimation is an important task in computer vision.Collecting data at scale for monocular depth estimation is challenging,as this task requires simultaneously capturing RGB images and depth information.Therefore,data augmentation is crucial for this task.Existing data augmentationmethods often employ pixel-wise transformations,whichmay inadvertently disrupt edge features.In this paper,we propose a data augmentationmethod formonocular depth estimation,which we refer to as the Perpendicular-Cutdepth method.This method involves cutting realworld depth maps along perpendicular directions and pasting them onto input images,thereby diversifying the data without compromising edge features.To validate the effectiveness of the algorithm,we compared it with existing convolutional neural network(CNN)against the current mainstream data augmentation algorithms.Additionally,to verify the algorithm’s applicability to Transformer networks,we designed an encoder-decoder network structure based on Transformer to assess the generalization of our proposed algorithm.Experimental results demonstrate that,in the field of monocular depth estimation,our proposed method,Perpendicular-Cutdepth,outperforms traditional data augmentationmethods.On the indoor dataset NYU,our method increases accuracy from0.900 to 0.907 and reduces the error rate from0.357 to 0.351.On the outdoor dataset KITTI,our method improves accuracy from 0.9638 to 0.9642 and decreases the error rate from 0.060 to 0.0598.
基金This work is financially supported by the National Natural Science Foundation of China (No. 10574085) Natural Science Foundation ofShanxi Province, China (No. 20041032).
文摘[FePt/Ag]n multilayers were deposited on glass substrates by RF magnetron sputtering and ex situ annealed at 550℃ for 30 min. The effects of inserted Ag layer thickness and the number of bilayer repetitions (n) on the structure and magnetic properties of the multilayers were investigated. It was found that the difference between in-plane and out-of-plane coercivities varied with an increase of inserted Ag layer thickness in the [FePt 2 nm/Ag x nm]10 multilayers. The ratio of out-of-plane coercivity to in-plane coercivity reached the maximum value with the Ag layer thickness of 5 nm, indicating that the Ag layer thickness plays an important role in obtaining perpendicular orientation. For the [FePt 2 nm/Ag 5 um]n multilayers, perpendicular orientation is also influenced by n. The maximum value of the ratio of out-of-plane coercivity to in-plane coercivity appeared when n was given as 8. It was found that the [FePt 2 nm/Ag 5 nm]8 had a high perpendicular coercivity of 520 kA/m and a low in-plane one of 88 kA/m, which shows a strong perpendicular anisotropy.
基金the National Key R&D Program of China(Grant No.2018YFB1306100)China Postdoctoral Science Foundation(Grant No.2019M653607)the Fundamental Research Funds for the Central Universities。
文摘Graphene-based materials on wearable electronics and bendable displays have received considerable attention for the mechanical flexibility,superior electrical conductivity,and high surface area,which are proved to be one of the most promising candidates of stretching and wearable sensors.However,polarized electric charges need to overcome the barrier of graphene sheets to cross over flakes to penetrate into the electrode,as the graphene planes are usually parallel to the electrode surface.By introducing electron-induced perpendicular graphene(EIPG)electrodes incorporated with a stretchable dielectric layer,a flexible and stretchable touch sensor with"in-sheet-chargestransportation"is developed to lower the resistance of carrier movement.The electrode was fabricated with porous nanostructured architecture design to enable wider variety of dielectric constants of only 50-μm-thick Ecoflex layer,leading to fast response time of only 66 ms,as well as high sensitivities of 0.13 kPa-1 below 0.1 kPa and 4.41 MPa-1 above 10 kPa,respectively.Moreover,the capacitance-decrease phenomenon of capacitive sensor is explored to exhibit an object recognition function in one pixel without any other integrated sensor.This not only suggests promising applications of the EIPG electrode in flexible touch sensors but also provides a strategy for internet of things security functions.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11247026 and 11374253)
文摘In a magnetic nanostripe, the effects of perpendicular magnetic anisotropy(PMA) on the current-driven horizontal motion of vortex wall along the stripe and the vertical motion of the vortex core are studied by micromagnetic simulations.The results show that the horizontal and vertical motion can generally be monotonously enhanced by PMA. However, when the current is small, a nonmonotonic phenomenon for the horizontal motion is found. Namely, the velocity of the horizontal motion firstly decreases and then increases with the increase of the PMA. We find that the reason for this is that the PMA can firstly increase and then decrease the confining force induced by the confining potential energy. In addition, the PMA always enhances the driving force induced by the current.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50831002,50971025,51071022,and11174031)the National Basic Research Program of China (Grant No. 2012CB932702)+3 种基金the Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT)the Beijing Nova Program (Grant No. 2011031)the Beijing Municipal Natural Science Foundation,China (Grant No. 2102032)the Fundamental Research Funds for the Central Universities
文摘Microstructures and magnetic properties of Ta/Pt/Co 2 FeAl(CFA)/MgO multilayers are studied to understand perpendicular magnetic anisotropy(PMA) of half-metallic full-Heusler alloy films.PMA is realized in a 2.5-nm CFA film with B2-ordered structure observed by a high resolution transmission electron microscope.It is demonstrated that a high quality interface between the ferromagnetic layer and oxide layer is not essential for PMA.The conversions between in-plane anisotropy and PMA are investigated to study the dependence of magnetic moment on temperature.At the intersection points,the decreasing slope of the saturation magnetization(M s) changes because of the conversions.The dependence of M s on the annealing temperature and MgO thickness is also studied.
基金supported by the State Key Project of Fundamental Research of Ministry of Science and Technology,China(Grant No.2010CB934400)the National Natural Science Foundation of China(Grant Nos.51229101 and 11374351)
文摘Recent progresses in magnetic tunnel junctions with perpendicular magnetic anisotropy (PMA) are reviewed and summarized. At first, the concept and source of perpendicular magnetic anisotropy (PMA) are introduced. Next, a historical overview of PMA materials as magnetic electrodes, such as the RE-TM alloys TbFeCo and GdFeCo, novel tetragonal manganese alloys Mn-Ga, L10-ordered (Co, Fe)/Pt alloy, multilayer film [Co, Fe, CoFe/Pt, Pd, Ni, AU]N, and ultra-thin magnetic metal/oxidized barrier is offered. The other part of the article focuses on the optimization and fabrication of CoFeB/MgO/CoFeB p-MTJs, which is thought to have high potential to meet the main demands for non-volatile magnetic random access memory.
文摘ZSM-5 plates with a perpendicular intergrowth structure was synthesized by using a simple amine as the structure directing agent under hydrothermal conditions,in which the mother plate and the perpendicularly standing plates oriented along the(010)and(100)planes of MFI crystals,respectively.During the crystallization process,the mother plate was initially formed on the surface of the amorphous solid gel,while a set of parallel plates perpendicularly grew on its surface,via a homogeneous nucleation mechanism.The mother plate and the perpendicular plates had a similar thickness of 100-200 nm and were characterized by considerably shortened straight and zigzag 10 member ring pores,respectively.This unique intergrowth structure greatly facilitated the diffusion of the reactive molecules in HZSM-5 crystals during methanol conversion to hydrocarbons.
文摘The present work is concerned with the problem of mode Ⅲ crack perpendicular to the interface of a bi-strip composite. One of these strips is made of a functionally graded material and the other of an isotropic material, which contains an edge crack perpendicular to and terminating at the interface. Fourier transforms and asymptotic analysis are employed to reduce the problem to a singular integral equation which is numerically solved using Gauss-Chebyshev quadrature formulae. Furthermore, a parametric study is carried out to investigate the effects of elastic and geometric characteristics of the composite on the values of stress intensity factor.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2017YFB0405701 and2018YFB0407601the National Natural Science Foundation of China under Grant Nos U1632264 and 11874349the Key Research Project of Frontier Science of the Chinese Academy of Sciences under Grant Nos QYZDY-SSW-JSC015 and XDPB12
文摘Off-stoichiometric full-Heusler alloy Co_2 MnAl thin films with different thicknesses are epitaxially grown on GaAs(001) substrates by molecular-beam epitaxy. The composition of the films, close to Co_(1.65)Mn_(1.35)Al(CMA),is determined by x-ray photoelectron spectroscopy and energy dispersive spectroscopy. Tunable perpendicular magnetic anisotropy(PMA) from 3.41 Merg/cm^3 to 1.88 Merg/cm^3 with the thickness increasing from 10 nm to 30 nm is found,attributed to the relaxation of residual compressive strain. Moreover, comparing with the ultrathin CoFeB/MgO used in the conventional perpendicular magnetic tunnel junction, the CMA electrode has a higher magnetic thermal stability with more volume involved. The PMA in CMA films is sustainable up to 300℃,compatible with semiconductor techniques. This work provides a possibility for the development of perpendicular magnetized full-Heusler compounds with high thermal stability and spin polarization.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFB0405700)the National Natural Science Foundation of China(Grant Nos.11474272 and 61774144)+1 种基金Beijing Natural Science Foundation Key Program,China(Grant No.Z190007)the Chinese Academy of Sciences(Grant Nos.QYZDY-SSW-JSC020,XDB44000000,and XDB28000000)。
文摘We demonstrate that radio frequency(RF)magnetron sputtering technique can modify the perpendicular magnetic anisotropy(PMA)of Pt/Co/normal metal(NM)thin films.Influence of ion irradiation during RF magnetron sputtering should not be neglected and it can weaken PMA of the deposited magnetic films.The magnitude of this influence can be controlled by tuning RF magnetron sputtering deposition conditions and the upper NM layer thickness.According to the stopping and range of ions in matter(SRIM)simulation results,defects such as displacement atoms and vacancies in the deposited film will increase after the RF magnetron sputtering,which can account for the weakness of PMA.The amplitude changes of the Hall resistance and the threshold current intensity of spin orbit torque(SOT)induced magnetization switching also can be modified.Our study could be useful for controlling magnetic properties of PMA films and designing new type of SOT-based spintronic devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62171013 and 61704005)the National Key Research and Development Program of China(Grant Nos.2021YFB3601303,2021YFB3601304,and 2021YFB3601300)+1 种基金the Beijing Municipal Science and Technology Project,China(Grant No.Z201100004220002)the Fundamental Research Funds for the Central Universities,China(Grant No.YWF-21-BJ-J-1043)。
文摘Spin-orbit torque(SOT)has been considered as one of the promising technologies for the next-generation magnetic random access memory(MRAM).So far,SOT has been widely utilized for inducing various modes of magnetization switching.However,it is a challenge that so many multiple modes of magnetization switching are integrated together.Here we propose a method of implementing both unipolar switching and bipolar switching of the perpendicular magnetization within a single SOT device.The mode of switching can be easily changed by tuning the amplitude of the applied current.We show that the field-like torque plays an important role in switching process.The field-like torque induces the precession of the magnetization in the case of unipolar switching,however,the field-like torque helps to generate an effective zcomponent torque in the case of bipolar switching.In addition,the influence of key parameters on the mode of switching is discussed,including the field-like torque strength,the bias field,and the current density.Our proposal can be used to design novel reconfigurable logic circuits in the near future.
文摘A 3-dimensional(3D)micromagnetic model combined with Fast Fourier Transform(FFT)method was built up to study the writability in the L1_(0)FePt perpendicular medium.The effects of controllable grain size distributions were studied by grain growth simulation.It is found that the cross-track-averaged magnetization changes little between the L1_(0)FePt medium with uniform or non-uniform grain size distribution.
文摘The single-pole tip (SPT) heads made of the high saturation FeCo ferromagnetic metals are crucial for the actualization of ultrahigh density perpendicular recording. The effective head field distribution in the medium is of key importance for the design of the SPT head, which would be analyzed by micromagnetic simulations in this work. Two 3D micromagnetic models of the SPT head were established to select a more appropriate method of modeling, with a magnetostatic image effect or a real soft magnetic material to model the image of the SPT head in soft under layer (SUL). The results from these two designs were tested and compared to the ideal head field calculated by the Jacobi finite element method (FEM); and the design with the real soft magnetic material as image was proved suitable for simulating the ultrahigh density perpendicular recording write head.
基金The present work has been partially supported by the Japanese Storage Research ConsortiumSupport by Beijing Science and Technology Nova Project(Grant No.H020821290120)is also appreciated.
文摘(FePt/Ag)n nano-multilayers were deposited on MgO (100) single crystal with laser ablation and then subjected to annealing. FePt L1o grains with (001) texture and thus a large perpendicular magnetic anisotropy constant Ku of the order of 106 J/m3 were formed. A thick Ag layer is found to be favorable for decreasing the dispersion of the easy axis for magnetization. The measurement of time decay of magnetization gave rise to a small activation volume of the order of 10-25m3, showing the promising of being the recording medium for future high density perpendicular recording.
基金This work was financially supported by the National Natural Science Foundation of China (No.50471093)the Science Founda-tion of Beijing (No.2052014)
文摘(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 anfiferromagnet (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.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50831002, 51271020, 50971025, 51071022, and 11174031)the National Basic Research Program of China (Grant No. 2012CB932702)+2 种基金PCSIRT, Beijing Nova Program, China (Grant No. 2011031)the Beijing Municipal Natural Science Foundation, China (Grant No. 2102032)the Fundamental Research Funds for the Central Universities, China
文摘Co2FeA10.5Si0.5 (CFAS)-based multilayers sandwiched by MgO layers have been deposited and annealed at different temperatures. Perpendicular magnetic anisotropy (PMA) with the magnetic anisotropy energy density Ku ≈2.5x106 erg/cm3 (1 erg = 10-7 J) and the coercivity He = 363 Oe (10e = 79.9775 A.m-1) has been achieved in the Si/SiO2/MgO (1.5 nm)/CFAS (2.5 nm)/MgO (0.8 nm)/Pt (5 nm) film annealed at 300 ℃. The strong PMA is mainly due to the top MgO layer. The structure can be used as top magnetic electrodes in half-metallic perpendicular magnetic tunnel junctions.
基金Project supported by the National Natural Science Foundation of China(Nos.11372175 and 11272197)the Doctoral Fund of Ministry of Education of China(No.20103108110004)the Innovation Program of Shanghai Municipality Education Commission(No.14ZZ095)
文摘The structures of water inside and outside (6,6), (8,8), and (10,10) single- walled carbon nanotubes (SWCNTs) under an electric field perpendicular to the tube axis are investigated by molecular dynamics simulations. The results show that dipole reorientation induced by electric field plays a significant role on the structures of confined water inside and outside SWCNTs. Inside SWCNTs, the average water occupancy and the average number of hydrogen bonds (H-bonds) per water molecule decrease as the electric intensity increases. Because the field intensity is sufficiently strong, the initial water structures inside the SWCNTs are destroyed, and the isolated water clusters are found. Outside SWCNTs, the azimuthal distributions of the density and the average number of H-bonds per water molecule around the solid walls become more and more asymmetric as the electric intensity increases. The percentages of water molecules involved in 0-5 H-bonds for all the three types of SWCNTs under different field intensities are displayed. The results show that those water molecules involved with most H-bonds are the most important to hold the original structures. When the electric field direction is parallel with the original preferred orientation, the density and the H-bond connections in water will be increased; when the electric field direction is perpendicular to the original preferred orientation, the density and the H-bond connections in water will be decreased.
基金Project supported by the National Natural Science Foundation of China(Grant No.11127406)
文摘In this article, we review the recent progress in growth, structural characterizations, magnetic properties, and related spintronic devices of tetragonal MnxGa and MnxA1 thin films with perpendicular magnetic anisotropy. First, we present a brief introduction to the demands for perpendicularly magnetized materials in spintronics, magnetic recording, and perma- nent magnets applications, and the most promising candidates of tetragonal MnxGa and MnxA1 with strong perpendicular magnetic anisotropy. Then, we focus on the recent progress of perpendicularly magnetized MnxGa and MnxA1 respec- tively, including their lattice structures, bulk synthesis, epitaxial growth, structural characterizations, magnetic and other spin-dependent properties, and spintronic devices like magnetic tunneling junctions, spin valves, and spin injectors into semiconductors. Finally, we give a summary and a perspective of these perpendicularly magnetized Mn-based binary alloy films for future applications.
基金supported by the National Basic Research Program of China (2014CB921104)the National Natural Science Foundation of China (Grant Nos. 51222103, 11274113, 11474067, and 51171047)the support from the Program for New Century Excellent Talents in University (NCET-12-0132)
文摘The exchange-coupled [Co/Ni]N/Tb Fe nano-magnetic films can display strong perpendicular magnetic anisotropy(PMA) which depends on the Tb:Fe component ratio, Tb Fe layer thickness and the repetition number N of [Co/Ni]Nmultilayer. Perpendicular spin valves in the nano thickness scale, consisting of a [Co/Ni]3free and a [Co/Ni]5/Tb Fe reference multilayer, show high giant magnetoresistance(GMR) signal of 6.5 % and a large switching field difference over3 k Oe. However, unexpected slanting of the free layer magnetization, accompanied by a reduced GMR ratio, was found to be caused by the presence of a thick Fe-rich or even a thin but Tb-rich Tb Fe layer. We attribute this phenomenon to the large magnetostriction effect of Tb Fe which probably induces strong stress acting on the free layer and hence reduces its interfacial PMA.