Tunneling Magnetoresistance Effect Research Articles

Tunneling magnetoresistance effect with controlled spin polarization based on Mn3ZnN

Abstract Due to groundbreaking advantages, antiferromagnetic offers superior prospects for the next-generation memory devices. However, detecting their Néel vector poses great challenges. Mn3ZnN, an antiperovskite antiferromagnetic, breaks TPτ and Uτ symmetries, exhibiting k-resolved spin polarization at Fermi surface. It’s ideal for electrodes to generate tunneling magnetoresistance (TMR) effects, which hinges on electrode-barrier compatibility. Testing various insulators, we obtained 2000% TMR effects in Mn3ZnN/SrTiO3/Mn3ZnN. Additionally, applying 2% biaxial stress increased the spin polarization to 35.24% in Mn3ZnN, hinting at higher TMR potential. These findings provide valuable insights for experimental and industrial developments in the field of spintronics.

First-principle study of CrO2-BNNT-CrO2 based MTJ device using EHTB model and its application in a MRAM circuit

In this work we investigated the performance of Single-Walled Boron Nitride Nanotube (SWBNNT) sandwiched between CrO2 based Magnetic Tunnel Junction (MTJ) structures with atomistic simulations. MTJ based device-level simulation was performed using the Extended Huckel based Tight Binding (EHTB) model. The SWBNNT as a dielectric layer and CrO2 as Ferromagnetic (FM) layers based Magnetic Tunnel Junction (MTJ) heterostructure was computed. The proposed MTJ device operates at the nano-Ampere (nA) range depicting its potential application in a low-powered nanoelectronics device. It also shows a promising Tunnel Magnetoresistance (TMR) effect. The practical circuit-level implementation of the proposed MTJ device in Magnetic Random-Access Memory (MRAM) was validated using LTspice. Hence, the calculated static power consumption and writing energy per bit was minimal for S1 and S2 based MRAM circuit. The perfect switching operation was depicted by the proposed MTJ device based MRAM.

Magnetic Switching Dynamics and Tunnel Magnetoresistance Effect Based on Spin-Splitting Noncollinear Antiferromagnet Mn3Pt

In comparison to ferromagnets, antiferromagnets are believed to have superior advantages for applications in next-generation magnetic storage devices, including fast spin dynamics, vanishing stray fields and robust against external magnetic field, etc. However, unlike ferromagnetic orders, which could be detected through tunneling magnetoresistance effect in magnetic tunnel junctions, the antiferromagnetic order (i.e., Néel vector) cannot be effectively detected by the similar mechanism due to the spin degeneracy of conventional antiferromagnets. Recently discovered spin-splitting noncollinear antiferromagnets, such as Mn3Pt with momentum-dependent spin polarization due to their special magnetic space group, make it possible to achieve remarkable tunneling magnetoresistance effects in noncollinear antiferromagnetic tunnel junctions. Through first-principles calculations, we demonstrate that the tunneling magnetoresistance ratio can reach more than 800% in Mn3Pt/perovskite oxides/Mn3Pt antiferromagnetic tunnel junctions. We also reveal the switching dynamics of Mn3Pt thin film under magnetic fields using atomistic spin dynamic simulation. Our study provides a reliable method for detecting Néel vector of noncollinear antiferromagnets through the tunnel magnetoresistance effect and may pave its way for potential applications in antiferromagnetic memory devices.

Structural design of magnetostrictive sensing glove and its application for gesture recognition

PurposeGesture recognition plays an important role in many fields such as human–computer interaction, medical rehabilitation, virtual and augmented reality. Gesture recognition using wearable devices is a common and effective recognition method. This study aims to combine the inverse magnetostrictive effect and tunneling magnetoresistance effect and proposes a novel wearable sensing glove applied in the field of gesture recognition.Design/methodology/approachA magnetostrictive sensing glove with function of gesture recognition is proposed based on Fe-Ni alloy, tunneling magnetoresistive elements, Agilus30 base and square permanent magnets. The sensing glove consists of five sensing units to measure the bending angle of each finger joint. The optimal structure of the sensing units is determined through experimentation and simulation. The output voltage model of the sensing units is established, and the output characteristics of the sensing units are tested by the experimental platform. Fifteen gestures are selected for recognition, and the corresponding output voltages are collected to construct the data set and the data is processed using Back Propagation Neural Network.FindingsThe sensing units can detect the change in the bending angle of finger joints from 0 to 105 degrees and a maximum error of 4.69% between the experimental and theoretical values. The average recognition accuracy of Back Propagation Neural Network is 97.53% for 15 gestures.Research limitations/implicationsThe sensing glove can only recognize static gestures at present, and further research is still needed to recognize dynamic gestures.Practical implicationsA new approach to gesture recognition using wearable devices.Social implicationsThis study has a broad application prospect in the field of human–computer interaction.Originality/valueThe sensing glove can collect voltage signals under different gestures to realize the recognition of different gestures with good repeatability, which has a broad application prospect in the field of human–computer interaction.

Electrically Controlled All-Antiferromagnetic Tunnel Junctions on Silicon with Large Room-Temperature Magnetoresistance.

Antiferromagnetic (AFM) materials are a pathway to spintronic memory and computing devices with unprecedented speed, energy efficiency, and bit density. Realizing this potential requires AFM devices with simultaneous electrical writing and reading of information, which are also compatible with established silicon-based manufacturing. Recent experiments have shown tunneling magnetoresistance (TMR) readout in epitaxial AFM tunnel junctions. However, these TMR structures are not grown using a silicon-compatible deposition process, and controlling their AFM order required external magnetic fields. Here it is shown three-terminal AFM tunnel junctions based on the noncollinear antiferromagnet PtMn3 , sputter-deposited on silicon. The devices simultaneously exhibit electrical switching using electric currents, and electrical readout by a large room-temperature TMR effect. First-principles calculations explain the TMR in terms of the momentum-resolved spin-dependent tunneling conduction in tunnel junctions with noncollinear AFM electrodes.

Temperature and bias voltage dependences of magnetic tunnel junction with FeAlSi electrode

We fabricated magnetic tunnel junctions (MTJs) with FeAlSi free layers and investigated the tunnel magnetoresistance (TMR) properties. We found that the temperature and bias voltage dependences of the TMR effect in FeAlSi-MTJs were almost the same as MTJs with Fe free layers despite the low Curie temperature of FeAlSi. In the inelastic electron tunneling spectroscopy measured at low temperatures, the relatively large cutoff energy of magnon excitation at the FeAlSi and MgO interface was confirmed. In addition, we studied for the first time the exchange stiffness constant of FeAlSi films by Brillouin light scattering. The determined value of the stiffness constant of FeAlSi was 14.3 (pJ/m), which was similar to that of Fe. Both the large magnon cutoff at the interface and the stiffness constant of FeAlSi are considered to be the reason for the good temperature and voltage dependences of FeAlSi-MTJs.

Arbitrary Modulation of Average Dwell Time in Discrete-Time Markov Chains based on Tunneling Magnetoresistance Effect

Arbitrary Modulation of Average Dwell Time in Discrete-Time Markov Chains based on Tunneling Magnetoresistance Effect

Magnetic-ferroelectric synergic control of multilevel conducting states in van der Waals multiferroic tunnel junctions towards in-memory computing.

van der Waals (vdW) multiferroic tunnel junctions (MFTJs) based on two-dimensional materials have gained significant interest due to their potential applications in next-generation data storage and in-memory computing devices. In this study, we construct vdW MFTJs by employing monolayer Mn2Se3 as the spin-filter tunnel barrier, TiTe2 as the electrodes and In2S3 as the tunnel barrier to investigate the spin transport properties based on first-principles quantum transport calculations. It is highlighted that apparent tunneling magnetoresistance (TMR) and tunneling electroresistance (TER) effects with a maximum TMR ratio of 6237% and TER ratio of 1771% can be realized by using bilayer In2S3 as the tunnel barrier under finite bias. Furthermore, the physical origin of the distinguished TMR and TER effects is unraveled from the k||-resolved transmission spectra and spin-dependent projected local density of states analysis. Interestingly, four distinguishable conductance states reveal the implementation of four-state nonvolatile data storage using one MFTJ unit. More importantly, in-memory logic computing and multilevel data storage can be achieved at the same time by magnetic switching and electrical control, respectively. These results shed light on vdW MFTJs in the applications of in-memory computing as well as multilevel data storage devices.

Magnetic Field Observation in a Magnetic Tunnel Junction by Scanning Transmission Electron Microscopy.

A magnetic tunnel junction (MTJ) consists of two ferromagnetic layers separated by a thin insulating layer. MTJs show tunnel magnetoresistance effect, where the resistance in the direction perpendicular to the insulator layer drastically changes depending on the magnetization directions (parallel or antiparallel) in the ferromagnetic layers. However, direct observation of local magnetizations inside MTJs have been challenging. In this study, we demonstrate direct observation of magnetic flux density distribution inside epitaxially grown Fe/MgO/Fe layers using differential phase contrast scanning transmission electron microscopy. By utilizing newly-developed tilt-scan averaging system for suppressing diffraction contrasts, we clearly visualize parallel and antiparallel states of ferromagnetic layers at nanometer resolution.

Giant tunnel magnetoresistance induced by thermal bias

We analyze the spin-resolved transport and, in particular, the tunnel magnetoresistance of an asymmetric ferromagnetic tunnel junction with an embedded quantum dot or molecule subject to thermal and voltage bias in the nonlinear response regime. We demonstrate that such system exhibits a giant tunnel magnetoresistance effect that can be tuned by gate and bias voltages. Large values of magnetoresistance are associated with the interplay between the Kondo correlations and the ferromagnetic-contact-induced exchange field. In particular, we show that the nonequilibrium current in the parallel and antiparallel magnetic configuration of the system changes sign at different values of the voltage and thermal bias. This gives rise to giant values of magnetoresistance, the sign of which can be controlled by the applied sources.

The role of ferromagnets and antiferromagnets for spintronic memory applications and their impact in data storage

The manipulation of multifunctional properties associated with ferromagnetic and antiferromagnetic materials has a great impact in information technology and digital data storage. A relatively recent field called spintronics is a promising alternative technology to store data more efficiently and to overcome obstacles that conventional electronics face. This article provides a small introduction to spintronic devices used for memory applications such as hard disk drives and MRAM, and details ways by which magnetization inside magnetic layers such as ferromagnets can be flipped. The giant magnetoresistance (GMR) effect and its successor in developing memory devices; the tunnelling magnetoresistance (TMR) effect are also discussed since they are key in developing magnetic memory devices.

Local density of states as a probe for tunneling magnetoresistance effect: Application to ferrimagnetic tunnel junctions

Local density of states as a probe for tunneling magnetoresistance effect: Application to ferrimagnetic tunnel junctions

Tunable magnetic anisotropy, half-metallicity and tunneling magnetoresistance effect of 2D CrI3 in CrI3/MnGeX3 (X = Se, Te) heterostructures under normal compressive strain

The induction of half-metallicity and tunable magnetic anisotropy of CrI3 monolayers remains challenging and unstable. In this study, we demonstrate that half-metallic CrI3 can be induced in a CrI3/MnGeX3(X = Se, Te) heterostructure. Normal compressive (NC) strain can effectively control the half-metallic band gap and spin-polarized electronic transport of CrI3 in CrI3/MnGeSe3. At 6% strain, the half-metallic band gap and equilibrium tunneling magneto-resistance (TMR) increases by 25% and 220%. The results of band structure, force theorem, charge density and work function calculations show that CrI3 in CrI3/MnGeSe3 loses electrons to form a hole-conducting half-metal with in-plane easy magnetization axis, while CrI3 gains electrons in CrI3/MnGeTe3 to form an electron-conducting half-metal with out-of-plane easy magnetization axis. Heterointerfacial half-metallicity in CrI3 is intrinsic without any external physical modification, and the NC strain of a two-dimensional structure can easily be realized experimentally, paving the way for further research of spintronic devices.

Large tunnel magnetoresistance in magnetic tunnel junctions with magnetic electrodes of metastable body-centered cubic CoMnFe alloys

A magnetic tunnel junction (MTJ) is a key device in spintronics applications, such as magnetoresistive random access memory (MRAM). Current standard magnetic material for MTJs is a body-centered cubic (bcc) FeCo(B), which shows large tunnel magnetoresistance (TMR) and high perpendicular magnetic anisotropy (PMA), both are crucial for high-memory capacities MRAM. It is demanded that magnetic materials showing TMR as well as PMA higher than FeCo(B) for further advance. One of alternative magnetic materials may be bcc Co since past ab-initio studies predict that bcc Co show large TMR effect in MgO-barrier MTJs and large PMA due to magneto-elastic effect for those strained state. However, bcc Co is thermodynamically unstable; thus, it is aimed to explore metastable bcc Co based alloys with high stability. Here, we propose metastable bcc Co based alloy with adding both Mn and Fe as a candidate. We study in-plane magnetized MTJs utilizing metastable bcc CoMnFe films as electrodes and demonstrate large TMR effect of 350% at 300 K and of 1002% at 5 K. This experimental finding will open a route to advanced bcc Co based magnetic material for MRAM applications.

Magnetic alignment technology for wafer bonding

PurposeWafer bonding is a key process for 3 D advanced packaging of integrated circuits. It requires very high accuracy for the wafer alignment. To solve the problems of large movement stroke, position calibration error and low production efficiency in optical alignment, this paper aims to propose a new wafer magnetic alignment technology (MAT) which is based on tunnel magneto resistance effect. MAT can realize micro distance alignment and reduces the design and manufacturing difficulty of wafer bonding equipment.Design/methodology/approachThe current methods and existing problems of wafer optical alignment are introduced, and the mechanism and realization process of wafer magnetic alignment are proposed. Micro magnetic column (MMC) marks are designed on the wafer by the semiconductor manufacturing process. The mathematical model of the space magnetic field of the MMC is established, and the magnetic field distribution of the MMC alignment is numerically simulated and visualized. The relationship between the alignment accuracy and the MMC diameter, MMC remanence, MMC thickness and sensor measurement height was studied.FindingsThe simulation analysis shows that the overlapping double MMCs can align the wafer with accuracy within 1 µm and can control the bonding distance within the micrometer range to improve the alignment efficiency.Originality/valueMagnetic alignment technology provides a new idea for wafer bonding alignment, which is expected to improve the accuracy and efficiency of wafer bonding.

Giant intrinsic magnetoresistance in spin-filtered tunnel junctions with ferrimagnetic electrode

In recent years, magnetic tunnel junctions (MTJs) have attracted strong research interest due to their potential use in nonvolatile memory technologies, such as magnetoresistive random access memory and magnetic logic applications. Half-metallic materials have been proposed as ideal electrode materials for MTJs to achieve large tunnel magnetoresistance (TMR) effects. Here, we design and investigate a spin-filter MTJ (sf-MTJ) consisting of a ferrimagnetic inverse Heusler alloy, ${\mathrm{Mn}}_{2}\mathrm{CoSi}$ as the electrode and CaS as the insulating tunnel barrier using ab initio quantum transport calculations. Our results demonstrate a high zero-bias voltage TMR ratio that initially oscillated before decreasing as the bias voltage increased. Despite the oscillatory TMR under bias voltage, the spin injection remains high and stable, highlighting the potential of sf-MTJs formed by ${\mathrm{Mn}}_{2}\mathrm{CoSi}$ electrodes for practical applications.

Tunnel magnetoresistance exceeding 100% in magnetic tunnel junctions using Mn-based tetragonal alloy electrodes with perpendicular magnetic anisotropy

We studied MgO barrier magnetic tunnel junctions (MTJs) comprising perpendicularly magnetized MnGa and FeCoB electrodes. In those perpendicular (p-) MTJs, we utilized thin metastable bcc CoMn alloys as an interlayer between MnGa and MgO to enhance the tunnel magnetoresistance (TMR) effect. Moreover, we investigated the effect of a thin Mg interlayer between MnGa and CoMn. Owing to the interlayer engineering, we achieved a TMR ratio over 100%, the highest value observed for p-MTJs with a tetragonal MnGa electrode. Our study contributes to the further development of spintronic devices using p-MTJs with various Mn-based tetragonal alloy electrodes.

Tremendous tunneling magnetoresistance effects based on van der Waals room-temperature ferromagnet Fe3GaTe2 with highly spin-polarized Fermi surfaces

Recently, van der Waals (vdW) magnetic heterostructures have received increasing research attention in spintronics. However, the lack of room-temperature magnetic order of vdW materials has largely impeded its development in practical spintronic devices. Inspired by the lately discovered vdW ferromagnet Fe3GaTe2, which has been shown to have magnetic order above room temperature and sizable perpendicular magnetic anisotropy, we investigate the basic electronic structure and magnetic properties of Fe3GaTe2 as well as tunneling magnetoresistance effect in magnetic tunnel junctions (MTJs) with structure of Fe3GaTe2/insulator/Fe3GaTe2 by using first-principles calculations. It is found that Fe3GaTe2 with highly spin-polarized Fermi surface ensures that such magnetic tunnel junctions may have prominent tunneling magnetoresistance effect at room temperature even comparable to existing conventional AlOx and MgO-based MTJs. Our results suggest that Fe3GaTe2-based MTJs may be the promising candidate for realizing long-waiting full magnetic vdW spintronic devices.

Inverse tunnel magnetoresistance of magnetic tunnel junctions with a NiCo2O4 electrode

Inverse spinel oxide NiCo2O4 (NCO) is known to exhibit ferrimagnetic characteristics and electrical conductivity. First-principles calculations predict NCO to be a half-metal with a negative polarization of −100%. In this study, we fabricated epitaxial NCO/MgO/Fe magnetic tunnel junctions by reactive molecular beam epitaxy and observed an inverse tunnel magnetoresistance (TMR) effect of −19.1% at 14 K, indicating that NCO has negative spin polarization. The TMR ratio monotonically decreased with increasing temperature, which was attributed to the temperature dependence of the NCO surface magnetization due to the thermal excitation of spin waves. In addition, the TMR ratio displayed strong bias voltage dependence, decreasing to less than half of the maximum value at +20 and −30 mV. These findings support the use of NCO in spintronic devices and should lead to further developments in oxide spintronics.

Generation of spin-polarized electronic currents using perpendicularly magnetized cobalt ferrite spin-filtering barriers grown on spinel-type-conductive layers

We demonstrated the generation of perpendicularly spin-polarized electronic currents using a tunnel spin-filtering effect through insulative Fe-rich cobalt ferrite CoxFe3−xO4+δ (I-CFO) barriers with perpendicular magnetic anisotropy (PMA). The I-CFO films grown on conductive Fe-rich cobalt ferrite CoyFe3−yO4 (C-CFO) films, which were deposited on additional I-CFO buffer layers on MgO(001) substrates, exhibited PMA induced by an epitaxial strain. Magnetic tunnel junctions (MTJs), which comprise C-CFO electrode layers, I-CFO barrier layers, and perpendicularly magnetized Co/{Tb/Co}15/Co spin detection layers, showed a tunnel magnetoresistance (TMR) effect. This indicated that spin-polarized tunnel currents were injected into the spin detection layers. A spin injection efficiency of −28% was observed for the MTJs with an I-CFO barrier of 3.0 nm in thickness at 100 K. The voltage dependence of the TMR effect indicates that the spin-injection efficiency is affected by voltage-dependent changes in the effective spin-dependent barrier width. The combination of spinel-type C-CFO and I-CFO films with well-controlled compositions and lattice strains is, therefore, applicable as a spin-injection source for spintronics devices when perpendicularly spin-polarized electronic currents are required.