High Tunnel Magnetoresistance Research Articles

Impact of Annealing Temperature on Tunneling Magnetoresistance Multilayer Stacks

The effect of annealing temperatures on the tunnel magnetoresistance (TMR) of MgO-based magnetic tunnel junctions (MTJs) has been investigated for annealing between 190 and 370°C. The TMR shows a maximum value of 215% at an annealing temperature of 330°C. A strong sensitivity of the TMR and the exchange bias of the pinned ferromagnetic layers on the annealing temperature are observed. Depending on sensor application requirements, the MTJ can be optimized either for stability and pinning strength or for a high TMR signal by choosing the appropriate annealing temperature. The switching mechanism of the ferromagnetic layers in the MTJ and the influence of the annealing on the layer properties, including the MgO barrier, are discussed.

Spin Transport Study in Chromium Trihalides CrCl3, CrBr3, and CrI3: an Ab Initio Study

First-principles investigations are performed on magnetic tunnel junctions (MTJs) constructed with chromium trihalide CrCl3 as barrier and half metallic ferromagnet (HMF) CrO2 as electrodes using density function theory (DFT) calculations, and the results are compared with CrBr3 and CrI3. On comparing the results obtained after performing the first-principles investigation on CrCl3, CrBr3, and CrI3, it is understood that CrCl3 offers very high tunnel magnetoresistance (TMR) of ~ 100% and spin injection efficiency (η) of ~ 100% for different bias voltages, and spin transport occurs due to tunneling which is evident from the transmission spectrum. Although CrBr3 has TMR greater than 95% and spin injection efficiency (η) of ~ 100%, transmission states are present at the Fermi level, hence, tunneling is not the phenomenon in the case of CrBr3. CrI3 suffers from fluctuations in both TMR and spin injection efficiency (η) over the applied bias voltage range and has more spin-up current and spin-down current in both parallel configuration and anti-parallel configuration. In CrI3, as there are states in transmission spectrum at the Fermi level, the spin transport occurs because of band-to-band hopping instead of tunneling. From the results obtained, CrCl3 is identified as the perfect material to be used as the barrier in MTJs.

Flexible CoFeB/MgO-based magnetic tunnel junctions annealed at high temperature (≥350 °C)

This study investigates the effect of high-temperature (350–500 °C) annealing on CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) directly formed on a flexible polyimide substrate, which has superior thermal tolerance. As the annealing temperature increases, the tunnel magnetoresistance (TMR) ratio enhances and reaches up to ∼200% at an annealing temperature of 450 °C. The annealing temperature dependence is similar to that of MTJs fabricated in the same way on a thermally oxidized silicon substrate. Images taken by a scanning transmission electron microscope confirm the improvement of the crystallization of the CoFeB and MgO layers, which can be an important factor in enhancing the TMR ratio. Furthermore, the endurance of the flexible MTJ against repeated stretching of its substrate is investigated. The TMR ratio shows no change during and after a 1000-cycle application of a tensile strain larger than 1%. The high TMR ratio and strain endurance demonstrated in this study suggest that the flexible MTJ structure is a promising candidate for a future strain-sensing device.

Measurement of Triaxial Magnetocardiography Using High Sensitivity Tunnel Magnetoresistance Sensor

Three-axis components of magnetocardiography (MCG) signals are measured with a high sensitivity tunnel magnetoresistance (TMR) sensor in this paper. From the measurement result, the R-wave and QRS-complex of MCG associated with the cardiac cycle are clearly observable without need of averaging. The T-wave is at the noise level and the weaker P-wave is drowned in noise. It is a great progress comparing with the previous MCG measurement with TMR sensor, where averaging was required to reliably detect R-wave. The amplitude of R-peak observed by the TMR sensor in the $x$ -direction is 200 pT, which is consistent with the measurement of superconducting quantum interference device (SQUID) considering the effect of distance from the observation point to the magnetic field source. The $y$ and $z$ components R-peak are about 550 pT. As the TMR sensor can measure MCG at room temperature, potentially, it is a promising alternative to cryogenically cooled superconducting devices to make inexpensive MCG instrumentation for extensive clinical applications.

Theoretical study on spintronic and spin caloritronic applications for equiatomic quaternary Heusler alloy NiCoMnAl

Equiatomic quaternary Heusler alloys (EQHAs) have received more and more attention in spintronic applications due to the half-metallicity and the long spin diffusion length. Recently, nearly half-metallicity (nearly 100% electronic spin polarization) and high Curie temperature (above 583 K) have been found in the equiatomic quaternary Heusler alloy of NiCoMnAl. In order to explore the potential spintronic applications, in this work, we design the magnetic tunnel junction (MTJ) of NiCoMnAl/InP/NiCoMnAl(0 0 1), and theoretically investigate the spin transport properties. It is shown that the MTJ exhibits a spin filtering effect and a high tunnel magnetoresistance ratio (up to 1.4 × 107%) when a bias voltage is applied to the electrodes of NiCoMnAl. Interestingly, without a bias voltage, a temperature difference can also drive the spin filtering effect. These versatile transport properties are discussed in terms of the half-metallicity of electrode, the spin-polarized transmission spectrum, and the difference of Fermi–Dirac distribution. The present work indicates promising applications for NiCoMnAl in spintronic devices and spin caloritronic devices.

Dependency of Multi-Level-Cell Behavior on Thickness of Top MgO Tunneling Barrier in Double Pinned Structure Perpendicular Spin-Torque-Transfer Magnetic Random Access Memory

These days dynamic-random-access-memory (DRAM) fabrication to scale down under 10-nm is complex which leads to high cost [1]. On the other hand, perpendicular spin-transfer-torque magnetic random access memory (p-STT MRAM) cell has a possibility of high-density integration with feature size of 4F2. Therefore, p-STT MRAM is the most powerful candidate of new memory instead of DRAM. In hence, p-STT MRAM requires high tunneling magnetoresistance (TMR) ratio greater than 150%, enough thermal stability (Δ=KuV/kBT) above 75 for a ten-year retention-time, and low switching current (J C0 ~ 1 MA/cm2) must be achieved for low power consumption [2-4]. However, the thermal stability is hard to maintain when the cell size is scaled down to 10 nm because the small volume of free layer leads to the changes of direction of spin by thermal agitation [5]. In this study, we designed a p-MTJ spin-valve with a double pinned structure to realize two-bit operation to overcome a larger scaling limit. We calculated four resistance states using relationship between the two different TMR of each MTJs. In particular, if the TMR of MTJ1 is half of MTJ2 and ratio of parallel resistance(Rp2/Rp1) is 0.8-0.9, the difference of each resistance state is equal. (see Fig. 1(b)) The TMR is mainly dependent on thickness of MgO tunnel barrier; therefore, we fabricated the p-MTJ spin-valve with a different thickness of MgO tunnel barrier (0.90 nm-1.35 nm) of MTJ1. Finally, we confirmed that the R-H curves match the four resistance states of p-MTJ with double pinned structure with our predicted results, and interval of resistance state is uniform when the thickness of top and bottom MgO are 1.36 nm and 1.10 nm as shown in Fig. 1(c). This implies that the double pinned p-MTJ spin-valve may be suitable for terabit integration compared to that of the single-bit operating p-STT MRAM memory cells. In the end, we report dependency of MLC behavior on thickness of top MgO tunneling barrier in double pinned structure pSTT MRAM. In addition, we present the MLC behavior of pSTT-MRAM with double pinned structure and show the thickness of top MgO for uniform resistance state. Acknowledgements This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No.2017R1A2A1A05001285) and Brain Korea 21 PLUS Program in 2014.

Large spin Hall effect and tunneling magnetoresistance in iridium-based magnetic tunnel junctions

Magnetic tunnel junctions (MTJs) switched by spin-orbit torque (SOT) have attracted substantial interest owing to their advantages of ultrahigh speed and prolonged endurance.Both field-free magnetization switching and high tunneling magnetoresistance (TMR) are critical for the practical application of SOT magnetic random access memory (MRAM).In this work, we propose an MTJ structure based on an iridium (Ir) bottom layer. Ir metal is a desirable candidate for field-free SOT switching owing to its strong intrinsic spin Hall conductivity (SHC), which can be enhanced via doping. Herein, we study TMR in Ir-based MTJs with symmetric and asymmetric structures.Ir-based MTJs exhibit large TMR, which can be further enhanced by heavy metal symmetry owing to the resonant tunneling effect. Our comprehensive investigations illustrate that Ir-based MTJs are promising candidates for realizing SOT switching and high TMR.

Study on the effect of re-deposition induced by ion beam etching on MTJ performances

Magnetic tunnel junction (MTJ) as a key spintronics device can be used for the high-sensitivity magnetic field sensor and high-density non-volatile magnetic random access memory (MRAM). To obtain a high tunneling magnetoresistance (TMR), precise control of the etching process for MTJs is an essential step. In order to investigate the effect of the etching angle on the performance of MTJ devices, a series of MTJ pillars are fabricated by etching with the incidence angle of 10°, 20° and 30°. The prepared samples are characterized by the optical microscopy and SEM, and the R-H curves are also measured and then statistically analyzed. The results reveal that the performance of the MTJ is strongly affected by the IBE process, displaying the uniformity of the pillars edge and MTJ performance will improve as well with the increase of the etching angle. Then, a simplified model based on the re-deposition effect of the etching process is established to explain the experimental phenomena. Furthermore, a newly defined material parameter is introduced in this model and obtained with fitting the experimental results. This proves a valuable way to evaluate the quality of the MTJ stack film without the interference of the device fabrication process.

High TMR for both in-plane and perpendicular magnetic field justified by CoFeB free layer thickness for 3-D MTJ sensors

We systematically studied the characteristics and influence of free layer thickness in magnetic tunnel junction (MTJ) with a perpendicular synthetic antiferromagnetic (p-SAF) reference layer on 8-inch wafer. The results show clearly that there is an optimal thickness of free layer to achieve the highest tunneling magnetoresistance (TMR) ratio of as high as 80.5% and 53.7% with perpendicular and in-plane magnetic field, respectively, while the resistance-area product (RA) reaches also highest value of 21.1 Ω*μm2. The thickness range of CoFeB to obtain perpendicular magnetic anisotropy (PMA) is determined. The variation of the magnetic moment of free layer indicates that the three-dimensional (3D) sensors can be designed by varying the thickness of the free layer and be controlled by the perpendicular and in-plane components through annealing under the in-plane magnetic field.

Sensing schemes for STT-MRAMs structured with high TMR in low RA MTJs

In this work, we investigated the sensing challenges of spin-transfer torque MRAMs structured with perpendicular magnetic tunnel junctions with a high tunneling magnetoresistance ratio in a low resistance-area product. To overcome the problems of reading this type of memory, we have proposed a voltage sensing amplifier topology and compared its performance to that of the current sensing amplifier in terms of power, speed, and bit error rate performance. We have verified that the proposed sensing scheme offers a substantial improvement in bit-error-rate performance. To enumerate the read operations of the proposed sensing scheme with the proposed cross-coupled capacitive feedback technique on the clamped circuity have successfully been performed a 2.5X reduction in average low power and a 13X increase in average reading speed compared with the previous works due to its device structure and the proposed circuit technique.

Perpendicular Spin-Transfer-Torque Magnetic Tunnel Junction Multi-Level Cell with Dual Free Layers and MgO Tunnel Barriers

Perpendicular spin-transfer-torque magnetic random access memory (p-STT-MRAM) is a promising candidate memory device for replacing dynamic random access memory (DRAM) facing with 10-nm sub scaling down. In addition to scaling down, p-STT MRAM has many advantages like fast write/read speed (~10ns) as DRAM, low power consumption (<1pJ), high endurance (>1014), and non-volatility (retention time > 10 years). But to replace DRAM, there are several challenges to be solved. First, high tunneling magneto-resistance (TMR) ratio for read sensing margin. Second, low critical current density(J C) for low power consumption. Third, thermal stability(Δ) for long retention time to save data. And also these parameters should be achieved at 350oC annealing temperature of the back-end-of line (BEOL) to be commercialized. Among them, thermal stability is closely related with cell size. As a cell size of MTJ decreases to achieve a high density memory device, thermal stability decreases with retention time, thus it is not easy to implement both high density and non-volatile memory device simultaneously by decreasing the cell size of MTJ. In our study to solve this issue, we propose the p-STT multi-level cell (MLC) magnetic tunnel junction (MTJ) because MLC MTJ can satisfy both high density and non-volatile memory device at the same time. In particular, we design the MTJ structure with dual free layers and MgO tunnel barriers, so that the MTJ can demonstrate four resistance states. In addition, we investigated the effect of the thickness of two free layers and MgO tunnel barriers on two magneto-resistance (MR) and switching voltage. In our experiments, the p-STT MTJ spin-valves were fabricated on 12-inch-diameter Si/ SiO2/W/TiN wafers by utilizing a 12-in. multi-chamber-cluster magnetron-sputtering system under a high vacuum (less than 110-8 Torr) without breaking the vacuum. Then, all samples were subject to ex-situ annealing at 350℃ at a back end of line (BEOL) for 30 minutes under a magnetic field of 3 tesla. In our presentation, we present how to optimize the thicknesses of two free layers and MgO tunnel barriers. In addition, we repot how the magnetic behavior and the resistance of MTJ is affected by magnetic and how the magneto-resistance of MTJ is closely related to the crystallinity of two MgO tunnel barriers. Acknowledgements This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2017R1A2A1A05001285)

First-principles study of a vertical spin switch in atomic scale two-dimensional platform

Abstract High in-plane charge carrier mobility and long spin diffusion length makes graphene a unique material for spin-based devices. However, in a vertical graphene junction, the 2pz orbitals of carbon atoms in graphene can be tuned via suitable magnetic substrates; this would affect the spin injection into graphene. Here, a vertical spin switch has been designed by embedding a single layer of graphene as a tunnel layer between the Ni (1 1 1) substrate. Periodic density functional approach in conjunction with Julliere’s model is used to calculate the tunnel magnetoresistance (TMR). Further, single-layered hexagonal Boron Nitride (h-BN) is sandwiched between the graphene and Ni (1 1 1) substrate to understand the role of hybridization at the interface on TMR. Our calculation shows that in contrast to the graphene junction, a much higher TMR value is obtainable in the case of the graphene/h-BN multi-tunnel junction (MTJ). The TMR in graphene junction is found to decrease with the increase of an externally applied electric field, and drops to zero for a field greater than equal to 0.16 V/A. Similar phenomenon was observed in the case of h-BN/graphene MTJ, where TMR value remains unchanged for electric field up to 0.1 V/A beyond which it drops to zero. The change in hybridization and charge-carrier-population at the interface modifies the magnetic exchange interaction and magnetic anisotropy resulting in a spin flip at interface, leads to rapid drop in TMR after a threshold electric field. The high and tunable TMR value suggests h-BN assisted high performance graphene based vertical spin switch.

Effect of insertion layer on electrode properties in magnetic tunnel junctions with a zero-moment half-metal

Due to its negligible spontaneous magnetization, high spin polarization and giant perpendicular magnetic anisotropy, Mn2RuxGa (MRG) is an ideal candidate as an oscillating layer in THz spin-transfer-torque nano-oscillators. Here, the effect of ultrathin Al and Ta diffusion barriers between MRG and MgO in perpendicular magnetic tunnel junctions is investigated and compared to devices with a bare MRG/MgO interface. Both the compensation temperature, Tcomp, of the electrode and the tunneling magnetoresistance (TMR) of the device are highly sensitive to the choice and thickness of the insertion layer used. High-resolution transmission electron microscopy, as well as analysis of the TMR, its bias dependence, and the resistance-area product allow us to compare the devices from a structural and electrical point of view. Al insertion leads to the formation of thicker effective barriers and gives the highest TMR, at the cost of a reduced Tcomp. Ta is the superior diffusion barrier which retains Tcomp, however, it also leads to a much lower TMR on account of the short spin diffusion length which reduces the tunneling spin polarization. The study shows that fine engineering of the Mn2RuxGa/barrier interface to improve the TMR amplitude is feasible.

The annealing effect on memory state stability and interlayer coupling in perpendicular magnetic tunnel junctions with ultrathin MgO barrier

Abstract Perpendicular magnetic tunnel junctions (p-MTJs) attract great interest because of their excellent performance in spin-transfer-torque magnetic random access memories (STT-MRAMs). The annealing process is critical to achieve the required structural and magnetic properties, therefore obtaining high perpendicular tunneling magnetoresistance (p-TMR) and lower switching current. In this work, the CoFeB/MgO/CoFeB-based p-TMR stack was prepared and a high p-TMR value of 155.9% was obtained from CIPT. The p-MTJs were patterned with pillar sizes ranging from 50 nm to 1000 nm and were annealed upon different annealing temperatures (TA) of 300 and 340 °C. The resistance at parallel (RP) and antiparallel (RAP) state in p-MTJs was obtained upon the application of a ±30 mT perpendicular magnetic field, where the angle of magnetization between storage and reference layer at memory state, θP and θAP, were derived from the P and AP resistance ratios with and without magnetic field. The condition θP = θAP of about 63.5° was found in as-deposited samples, indicating a ferromagnetic interlayer coupling between storage and reference layers, where θP = 0° and θAP = 180° at TA = 300 °C and 340 °C demonstrate a stable memory state. The stability of the resistance state was modeled by considering the evolution of effective perpendicular magnetic anisotropy (Keff) and interlayer coupling constant (J), showing a method to evaluate the ratio of Keff/J via the memory state resistance characterization, where the Keff/J of about −1.26 was obtained in our as-deposited samples. Our study assesses the effect of TA on the θP and θAP and supplies the method to enhance the stability through the optimization of perpendicular magnetic anisotropy and interlayer coupling, so to better control the performance of p-MTJ-based STT-MRAMs.

Giant nonvolatile manipulation of magnetoresistance in magnetic tunnel junctions by electric fields via magnetoelectric coupling

Electrically switchable magnetization is considered a milestone in the development of ultralow power spintronic devices, and it has been a long sought-after goal for electric-field control of magnetoresistance in magnetic tunnel junctions with ultralow power consumption. Here, through integrating spintronics and multiferroics, we investigate MgO-based magnetic tunnel junctions on ferroelectric substrate with a high tunnel magnetoresistance ratio of 235%. A giant, reversible and nonvolatile electric-field manipulation of magnetoresistance to about 55% is realized at room temperature without the assistance of a magnetic field. Through strain-mediated magnetoelectric coupling, the electric field modifies the magnetic anisotropy of the free layer leading to its magnetization rotation so that the relative magnetization configuration of the magnetic tunnel junction can be efficiently modulated. Our findings offer significant fundamental insight into information storage using electric writing and magnetic reading and represent a crucial step towards low-power spintronic devices.

CrO2-based heterostructure and magnetic tunnel junction: perfect spin filtering effect, spin diode effect and high tunnel magnetoresistance

Half-metallic ferromagnetic CrO2 has attracted much interest due to its 100% spin polarization and high Curie temperature. CrO2 films have been fabricated on a TiO2 (100) substrate. However, there have been no reports on the spin transport properties of devices based on a CrO2 electrode and TiO2 barrier. In this work, we use first-principles calculations combined with a nonequilibrium Green's function method to investigate the bias-voltage-dependent spin transport properties for the CrO2/TiO2 (100) heterostructure and the CrO2/TiO2/CrO2 (100) magnetic tunnel junction (MTJ). Our results reveal the excellent spin filtering effect and spin diode effect in the heterostructure as well as the high tunnel magnetoresistance ratio (up to 4.48 × 1014%) in the MTJ, which indicate potential spintronic applications. The origins of these perfect spin transport characteristics are discussed in terms of the calculated spin-dependent electrode band structures, the spin-dependent transmission spectra and semiconductor theory.

Enhancement of Perpendicular Magnetic Anisotropy Through Fe Insertion at the CoFe/W Interface

Magnetic tunnel junctions (MTJs) based on MgO/CoFeB/W structures are of particular interest for magnetic random access memories due to their high tunnel magnetoresistance, low damping, and stable properties at high annealing temperature. One of the major challenges is to obtain a strong interfacial perpendicular magnetic anisotropy (PMA) for sufficient thermal stability during data storage. Here we investigate magnetic anisotropy energies (MAEs) in the ferromagnet (FM)/W structure with different FM materials and interface insertions. We find that the Fe/W interface exhibits a remarkable PMA, whereas the Co/W interface displays a large in-plane anisotropy, which reduces the PMA in the MgO/CoFeB/W structure. By inserting a thin Fe layer at the CoFe/W interface, the interfacial PMA can be enhanced to 3.34 mJ/m2. Microscopic mechanism behind these phenomena is explained with the changes of orbital-resolved MAEs due to the charge redistribution at the interface. These findings pave a new way for the enhancement of PMA and point toward the possibility of achieving high thermal stability in small-node MTJs.

Enhanced Annealing Stability of Exchange-Biased Pinned Layer in Magnetic Tunnel Junction Using Ta/Ru/Ta/Ru Underlayer

To realize highly sensitive analog sensor using magnetic tunnel junctions (MTJs), there is a demand for MgO-MTJs with a high signal-to-noise ratio. Thermal annealing is important for improving the crystalline quality of MgO barrier in order to enhance the tunneling magnetoresistance (TMR) ratio and decrease the noise level of MTJs. However, annealing at excessively high temperatures causes degradation of the exchange bias field ( $H_{\text {ex}}$ ) in the exchange-biased pinned layer (EB-PL). In this paper, we aim to develop a MgO-MTJ with high annealing stability by investigating the effect of underlayer structure on the annealing stability of EB-PL in MTJs. We fabricated two types of MTJ, one with a Ta/Ru underlayer (TR-UL) and one with a Ta/Ru/Ta/Ru underlayer (TRTR-UL). The results of evaluating the $H_{\text {ex}}$ of MTJs annealed in the temperature range of 320 °C–420 °C found that the MTJ containing a TRTR-UL (TRTR-MTJ) has higher annealing stability compared with that of the MTJ containing a TR-UL (TR-MTJ). Furthermore, the results of measuring the TMR ratio and 1/ $f$ noise level of the MTJs annealed at 380 °C showed that the TRTR-MTJ exhibits a higher TMR ratio and lower noise level than the TR-MTJ. To determine the mechanism by which the annealing stability improves, we carried out microstructural analysis of both MTJs and found that thermal Mn diffusion in the TRTR-MTJ was smaller than that in the TR-MTJ, and the crystallinity of IrMn on the TRTR-UL was found to be clearly improved compared with that on the TR-UL. As a result of $d$ -spacing analysis of each layer in the TRTR-UL, the second Ta layer deposited on the Ru layer was found to have $d$ -spacing corresponding to the (110) textured $\alpha $ -Ta structure and to be highly crystalline, whereas the first Ta layer was not found to have the components of (110) textured $\alpha $ -Ta structure. These results indicate that the Ta-on-Ru structure is responsible for the high crystallinity of the IrMn layer disposed on the TRTR-UL, resulting in the high annealing stability thanks to small Mn diffusion.

Single-molecule tunnel magnetoresistance of azulene

The single-molecule electric current in azulene sandwiched between ferromagnetic nickel electrodes was calculated by first-principles calculation. Varying the magnetic configuration of the electrodes provided a change in electric current to produce tunnel magnetoresistance (TMR). Compared to naphthalene, azulene had a relatively high TMR ratio in the low bias range from −0.2 V to 0.2 V. Moreover, the electric current of the oligomers of azulene was calculated. The oligomers did not significantly decrease the electric current compared to azulene and maintained the TMR ratio in the low bias range. The smaller energy gap of azulene compared to that of naphthalene increased the transmittance at the Fermi level that resulted in a steep change in the electric current upon varying the magnetic configuration of the electrodes.

Strain-Mediated Spin-Orbit-Torque Switching for Magnetic Memory

Spin-orbit torque (SOT) represents an energy efficient method to control magnetization in magnetic memory devices. However, deterministically switching perpendicular memory bits usually requires the application of an additional bias field for breaking lateral symmetry. Here we present a new approach of field-free deterministic perpendicular switching using a strain-mediated SOT switching method. The strain-induced magnetoelastic anisotropy breaks the lateral symmetry, and the resulting symmetry-breaking is controllable. A finite element model and a macrospin model are used to numerically simulate the strain-mediated SOT switching mechanism. The results show that a relatively small voltage (${\pm}0.5$ V) along with a modest current ($3.5 \times 10^{7} A/cm^{2}$) can produce a 180{\deg} perpendicular magnetization reversal. The switching direction (up or down) is dictated by the voltage polarity (positive or negative) applied to the piezoelectric layer in the magnetoelastic/heavy metal/piezoelectric heterostructure. The switching speed can be as fast as 10 GHz. More importantly, this control mechanism can be potentially implemented in a magnetic random-access memory system with small footprint, high endurance and high tunnel magnetoresistance (TMR) readout ratio.