Search

We investigate the junction size dependence of magnetic properties of a CoFeB free layer in CoFeB/MgO magnetic tunnel junctions (MTJs) by homodyne-detected ferromagnetic resonance, where the diameter of the circular MTJs is varied from 35 nm to 100 nm. We observe the increase of the effective perpendicular magnetic anisotropy field and the apparent damping constant in the free layers with decreasing diameter. [ABSTRACT FROM AUTHOR]

We investigate spin-wave resonance in nanoscale CoFeB/MgO magnetic tunnel junctions (MTJs) with a perpendicular easy axis and various free-layer sizes. Two types of MTJs are fabricated by different process conditions, and the spin-wave resonance is measured with homodyne-detected ferromagnetic resonance. We focus on the distance between resonance frequencies of the uniform and spin-wave modes as a function of the free-layer size in order to examine the effect of the edge state of MTJs. A marked difference is observed between the two types of MTJs, and the result is consistently reproduced by a model assuming free- or fixed-edge boundary conditions with or without reduced magnetic properties near the pattern edge for each MTJ. The obtained results indicate that the edge state of nanoscale MTJs is crucially affected by the process condition, and spin-wave resonance can serve as a sensitive probe for the edge condition. [ABSTRACT FROM AUTHOR]

We report here the results of two-dimensional electron gas based micro-Hall magnetometry measurements and micromagnetic simulations of dipolar coupled nanomagnets of Ni80Fe20 arranged in a double square ring-like geometry. We observe that although magnetic force microscopy images exhibit single domain like magnetic states for the nanostructures, their reversal processes may undergo complex behavior. The details of such reversal behavior are observed as specific features in micro-Hall magnetometry data, which are comparable with the micromagnetic simulation data. [ABSTRACT FROM AUTHOR]

We investigate the influence of naturally grown 2-5 nm thin surface layer of antiferromagnetic (AFM) Cr2O3 on the half metallic ferromagnet CrO2 by measuring the magnetic behavior of a single micro-crystal. The temperature variation of the magnetic stray fields of the micro-crystal measured by micro-Hall magnetometry shows an anomalous increase below ∼60 K. We find clear evidence that this behavior is due to the influence of the AFM surface layer. The average amplitude of the Barkahausen jumps exhibits a similar temperature dependence indicating that the AFM surface layer plays a role in defining the potential landscape seen by the domain configuration in the ferromagnetic grain. [ABSTRACT FROM AUTHOR]

We have determined the material parameters of optimized synthetic ferrimagnet (SyF) free layers in magnetic tunnel junctions by means of magneto-resistance loops as well as microwave noise spectroscopy under constant voltage, and the field dependence thereof. By comparing the experimental data with calculated loops and spin wave modes from a 2-macrospin model, we have deduced the saturation magnetization, anisotropy, damping, and interlayer exchange coupling. From waiting time experiments of field-induced switching, the energy barrier relevant for the thermally activated switching of the free SyF has been experimentally evaluated and compared to an existing model in order to assess its consistency. [ABSTRACT FROM AUTHOR]

The microstructure of pseudo spin-valve magnetic tunnel junctions (MTJs) comprising a stacking structure of Ta/Ru/Ta/CoFeB/MgO/CoFeB/ with and without X = Pd, Ti, Ta fabricated on thermally oxidized Si wafer with different annealing temperatures, Ta = 250 °C, 300 °C, 400 °C, and 500 °C, has been investigated. The as-deposited MTJs exhibit an amorphous CoFeB structure that crystallizes into bcc Fe-Co (001) from the MgO (001) interface upon annealing at Ta ≥ 250 °C. A bcc Fe-Co (110) crystallizes from the fcc Pd (111) interface. The Fe-Co layer is alloyed with Pd layer at Ta = 500 °C to form an (Fe, Co)-Pd alloy layer, which causes a drastic reduction in the tunneling magnetoresistance (TMR) from 171% to -2.7%. In the Ti capped MTJs, bcc Fe-Co (001) crystallizes from the hcp (001) Ti interface at Ta = 300 °C. Upon further annealing to Ta ≥ 400 °C, the Ti oxidizes to form amorphous Ti-Ox. The rejected B diffuses back to the CoFe layer at Ta = 500 °C that degrades the TMR. On the other hand, the Ta capped MTJs annealed at 300 ≤ Ta ≤ 500 °C show a perfect grain-to-grain epitaxy with an orientation relationship of (001)[110]MgO//(001)[100]CoFe without interdiffusion or oxidation, resulting in the highest TMR value among all the MTJs with various capping layers. [ABSTRACT FROM AUTHOR]

We have investigated the microstructure and local chemistry of Ta/Ru/Ta/CoFeB/MgO/CoFeB/Ta/Ru magnetic tunnel junctions with different values of tunneling magnetoresistance (TMR) as a result of annealing at different temperatures. Annealing at 500 °C led to the templated crystallization of the amorphous CoFeB layer having coherent interfaces with MgO grains with an orientation relationship of <001>[011]MgO∥<001>[001]CoFe, and the B rejected from crystallized CoFeB was found to be dissolved in upper amorphous Ta layers and segregated in the bottom crystalline Ta layer. Annealing at 600 °C led to the dissolution of 3–4 at. % Ta in the MgO barrier, and B was found to be segregated at the CoFeB/MgO and Ta/Ru interfaces as a result of the crystallization of the top amorphous Ta layer. Further degradation in TMR of the samples annealed at 650 °C results from the loss of bcc-CoFe (001) texture in the bottom CoFeB electrode due to the pronounced Ta diffusion into the CoFe/MgO/CoFe layers. [ABSTRACT FROM AUTHOR]

We present a direct and quantitative method to measure the current-induced fieldlike torques in current perpendicular to plane magnetic multilayers. We illustrate this method on nanopillars patterned from MgO-based magnetic tunnel junctions. By measuring how the Stoner astroids are displaced, shrinked, and distorted under the influence of a bias current, we separate the contributions of the current-induced fieldlike torque, the current-induced heating, and the current-induced spin torque. In contrast to high frequency based measurement methods that are better suited to analyze the spin torque than the fieldlike term, our measurement is direct and quantitative for the current-induced fieldlike term and the heating induced reduction in shape anisotropy, while only qualitative for the spin torque. [ABSTRACT FROM AUTHOR]

We have measured the distribution of switching times in spin-transfer switching induced by fast current pulses in two pillar-shaped systems: (i) spin valves and (ii) MgO-based magnetic tunnel junctions. (i) Spin valves can sustain high currents, such that the application of pulsed currents of amplitude a few times that of the static switching threshold is possible. This makes subnanosecond switching within reach. In that limit, the pulse durations leading to switching follow a multiply stepped distribution at 300 K and a regular distribution at 40 K. At 300 K, this reflects the precessional nature of the switching, which proceeds through a small number of precession cycles. The switching time distribution can be modeled from the thermal variance of the initial magnetization orientations. At 40 K, nonuniform magnetization switching occurs. (ii) In MgO-based tunnel junctions, we could follow individual time-resolved switching events with a 13 GHz bandwidth. The switching proceeds through a nanosecond-scale random incubation delay during which the resistance is quiet, followed by a sudden (400 ps duration) transition terminated by a pronounced ringing that is damped within 1.5 ns. While the incubation delay is probabilistic, the following time dependence of the resistance is reproducible. [ABSTRACT FROM AUTHOR]

Thin-film transistors (TFTs) made of transparent channel semiconductors such as ZnO are of great technological importance because their insensitivity to visible light makes device structures simple. In fact, there have been several demonstrations of ZnO TFTs achieving reasonably good field effect mobilities of 1–10 cm2/V s, but the overall performance of ZnO TFTs has not been satisfactory, probably due to the presence of dense grain boundaries. We modeled grain boundaries in ZnO TFTs and performed simulation of a ZnO TFT by using a two-dimensional device simulator in order to determine the grain boundary effects on device performance. Polycrystalline ZnO TFT modeling was started by considering a single grain boundary in the middle of the TFT channel, formulated with a Gaussian defect distribution localized in the grain boundary. A double Schottky barrier was formed in the grain boundary, and its barrier height was analyzed as a function of defect density and gate bias. The simulation was extended to TFTs with many grain boundaries to quantitatively analyze the potential profiles that developed along the channel. One of the main differences between a polycrystalline ZnO TFT and a polycrystalline Si TFT is that the much smaller nanoscaled grains in a polycrystalline ZnO TFT induces a strong overlap of the double Schottky barriers with a higher activation energy in the crystallite and a lower barrier potential in the grain boundary at subthreshold or off-state region of its transfer characteristics. Through the simulation, we were able to estimate the density of total trap states localized in the grain boundaries for polycrystalline ZnO TFT by determining the apparent mobility and grain size in the device. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This research is an attempt to apply thermal plasma chemical vapor deposition for the ultrafast deposition of Si films for solar cells. The improvement of stability, controllability, and cleanliness of the process enabled the deposition of μc-Si films at the ultrafast rate of over 1000 nm/s. Moreover, a minimum defect density of 7.2x10[sup 16] cm[sup -3] was achieved. Monte-Carlo simulation and step coverage analysis suggested that the precursor is an approximately 1 nm cluster with a sticking probability of about 0.6. The success of this research may change the established concepts of Si deposition technology. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have investigated thin (In, Mn)As layer and (In, Mn)As quantum dots (with Mn mole fraction lower than 0.02) on GaAs(001) by fluorescence extended x-ray absorption fine structure (EXAFS) in order to study the local structures formed around the Mn atoms. The EXAFS analysis revealed that in a 10 nm thick (In, Mn)As layer, the In-site substitutional Mn and the NiAs-type MnAs coexisted, while the majority of the Mn atoms were substituted in the In-sites of InAs in (In, Mn)As quantum dots. It is considered that different growth modes for the thin layer and the quantum dots affect the local structures. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Provides information on a study which reviewed the growth, magnetotransport and magnetic properties of gallium-magnesium-arsenic ((Ga,Mn)As) alloys. Preparation of (Ga,Mn)As; Magnetic properties; Spin-dependent tunneling in resonant tunneling structures.

We report on the magnetoresistive effects in a metallic antiferromagnet (AFM)/nonmagnet (NM) PtMn/Pt heterostructure with varying thickness of PtMn (1 nm ≤ tPtMn ≤ 10 nm). Longitudinal magnetoresistive effects are measured for magnetic field rotations along three mutually perpendicular directions. The results show a transformation in the functional dependencies with the increase in tPtMn and are attributed to the spin Hall magnetoresistive effects arising from the interaction of spin currents generated by Pt with the antiferromagnetic PtMn. The present findings with appreciable magnetoresistive effects in an AFM/NM metallic heterostructure add yet another option of the material system for antiferromagnetic spintronics. [ABSTRACT FROM AUTHOR]

We investigate the magnetic properties of a MgO/CoFeB/Ta/CoFeB/MgO/capping-layer (Ru or Ta) structure and properties of a magnetic tunnel junction with the structure as a free layer. By using Ru instead of Ta as the capping layer, interfacial anisotropy Ki increases by a factor of ∼2 and a smaller damping constant is obtained. The increase in Ki results in an enhancement of the thermal stability factor of the free layer with the Ru capping layer compared with that with the Ta capping layer in magnetic tunnel junctions. [ABSTRACT FROM AUTHOR]

Presents a study that examined a class of diluted magnetic semiconductor (DMS) based on a III-V semiconductor. Growth of DMS through low temperature molecular beam epitaxy; Homogeneous incorporation of manganese (Mn) in the films under certain growth conditions; Magnetic measurements and x-ray diffraction.

The bit-to-bit distribution of a critical current density for magnetic domain wall (DW) motion is studied using Co/Ni wires with various wire widths (ws). The distribution inherently decreases with the w, and the ratio of standard deviation to average is 9.8% for wires with w=40 nm. It is found that a self-distribution within one device, which is evaluated through repeated measurement, is a dominant factor in the bit-to-bit distribution. Micromagnetic simulation reveals that the distribution originates from DW configuration, which varies with device size. [ABSTRACT FROM AUTHOR]

The robustness of data load of metal-oxide-semiconductor/magnetic tunnel junction (MOS/MTJ) hybrid latches at power-on is examined by using Monte Carlo simulation with the variations in magnetoresistances for MTJs and in threshold voltages for MOSFETs involved in 90 nm technology node. Three differential pair type spin-transfer-torque-magnetic random access memory cells (4T2MTJ, 6T2MTJ, and 8T2MTJ) are compared for their successful data load at power-on. It is found that the 4T2MTJ cell has the largest pass area in the shmoo plot in TMR ratio (tunnel magnetoresistance ratio) and Vdd in which a whole 256 kb cell array can be powered-on successfully. The minimum TMR ratio for the 4T2MTJ in 0.9Vdd<1.9V is 140%, while the 6T2MTJ and the 8T2MTJ cells require TMR ratio larger than 170%. [ABSTRACT FROM AUTHOR]

We investigate properties of magnetic tunnel junctions (MTJs) having a Co/Pt multilayer as a recording layer. A CoFeB layer is inserted between MgO barrier and the recording layer in order to enhance the tunnel magnetoresistance ratio. We show that an additional layer of Ta inserted between CoFeB and Co/Pt multilayer is effective in improving the MTJ properties after annealing. A high effective magnetic anisotropy energy per unit area over 1.2 mJ/m² is obtained after annealing at 300 °C. Using a 1.6 nm-thick CoFeB insertion layer, both high thermal stability factor of 92 and high tunnel magnetoresistance ratio of 91% are achieved in a MTJ with 17 nm in diameter. [ABSTRACT FROM AUTHOR]

We investigate in-plane current-induced magnetization reversal under an in-plane magnetic field in Hall bar shaped devices composed of Ta/CoFeB/MgO structures with perpendicular magnetic easy axis. The observed relationship between the directions of current and magnetization switching and Ta thickness dependence of magnetization switching current are accordance with those for magnetization reversal by spin transfer torque originated from the spin Hall effect in the Ta layer. [ABSTRACT FROM AUTHOR]

We demonstrated read and write characteristics of a three terminal memory device with a perpendicular anisotropy-free layer of a strip of [Co/Ni] and a low-switching perpendicularanisotropy CoFeB/MgO sensing layer. This new design of the cell results in a small cell area. The switching magnetic field of the sensing layer can be decreased by changing sputtering gas for the Ta-cap from Ar to Kr. An electron energy-loss spectroscopy analysis of the cross-section of the magnetic tunneling junction (MTJ) revealed that the boron content in CoFeB with a Kr-sputtered Ta-cap was smaller than that with an Ar-sputtered one. A change in resistance for the MTJ was observed that corresponded to the magnetic switching of the Co/Ni wire and its magnetoresistance ratio and critical current were 90% and 0.8 mA, respectively [ABSTRACT FROM AUTHOR]

This paper describes the possibility of a switching upset of a magnetic tunnel junction (MTJ) caused by a terrestrial radiation-induced single-event-upset (SEU) current in spintronic integrated circuits. The current waveforms were simulated by using a 3-D device simulator in a basic circuit including MTJs designed using 90-nm CMOS parameters and design rules. The waveforms have a 400 -μA peak and a 200-ps elapsed time when neutron particles with a linear energy transfer value of 14MeV cm2/mg enter the silicon surface. The authors also found that the SEU current may cause soft errors with a probability of more than 10-12 per event, which was obtained by approximate solution of the ordinary differential equation of switching probability when the intrinsic critical current (IC0) became less than 30 μA [ABSTRACT FROM AUTHOR]

A compact nonvolatile programmable switch (NVPS) using 90 nm CMOS technology together with perpendicular magnetic tunnel junction (p-MTJ) devices is fabricated for zero-standby-power field-programmable gate array. Because routing information does not change once it is programmed into an NVPS, high-speed read and write accesses are not required and a write-control transistor can be shared among all the NVPSs, which greatly simplifies structure of the NVPS. In fact, the effective area of the proposed NVPS is reduced by 40% compared to that of a conventional MTJ-based NVPS. The instant on/off behavior without external nonvolatile memory access is also demonstrated using the fabricated test chip. [ABSTRACT FROM AUTHOR]

The effect of B concentration on the tunneling magnetoresistance (TMR) of (Co25Fe75)100-xBx/MgO/(Co25Fe75)100-xBx (x = 22 and 33) pseudo-spin-valve (P-SV) magnetic tunnel junctions (MTJs) was investigated. The TMR ratios for optimally annealed MTJs with x = 22 and 33 were 340% and 170%, respectively, at room temperature. High resolution transmission electron microscopy (HRTEM) observation showed a weaker (001) texture in the MgO barrier in the MTJ with x = 33. The bottom electrode was not fully crystallized even with a considerable amount of B in the (Co25Fe75)67B33, while good epitaxy was observed between (001) textured MgO and (Co25Fe75)78B22 electrodes. [ABSTRACT FROM AUTHOR]

ac susceptibility of a ferromagnetic semiconductor (Ga,Mn)As was measured using microscaled Hall bar through the anomalous Hall effect. The synchronous component of the Hall resistance with applied ac magnetic field (∼1 mT) was detected using a lock-in technique. The temperature dependence of the ac Hall resistance shows a clear peak in the vicinity of the Curie temperature TC, when an offset dc field, whose magnitude is comparable to that of the ac field, is superimposed. We applied this method to detect the change of TC as a function of hole concentration by applying electric fields. [ABSTRACT FROM AUTHOR]

We have investigated the magnetic and the crystalline properties of a set of Ga1-xMnxAs layers with high nominal Mn compositions (x=0.101–0.198). Magnetization measurements and combined channeling Rutherford backscattering (c-RBS) and particle induced x-ray emission (c-PIXE) measurements have been performed to determine the effective Mn composition xeff and the fraction of Mn atoms at various lattice sites. Here, xeff determined from magnetization measurements, which increases with increasing x, is consistent with the results determined from c-RBS-PIXE measurements. [ABSTRACT FROM AUTHOR]

The authors have fabricated field-effect transistor structures with a ferromagnetic Ga1-xMnxAs channel having Mn composition of x=0.027–0.200. The samples with larger x have higher Curie temperature TC and hole concentration p, while the controllable range of TC by applying external electric field does not increase with x. x dependence of effective Mn composition is also described. [ABSTRACT FROM AUTHOR]

We investigate a variation of magnetic domain pattern in demagnetized perpendicular-easy-axis CoFeB/MgO stacks with a wide-range electric field and discuss the electric-field effect on the exchange stiffness constant AS. We observe a non-linear variation of domain period DP with the applied electric field, in contrast to the effective perpendicular anisotropy field HKeff that is evaluated from a ferromagnetic resonance and shows a linear response. An analysis based on a model describing the relation of DP to AS and HKeff suggests that AS varies non-linearly with the electric field, implying an involved characteristic mechanism of the exchange stiffness in the studied systems. A possible scenario for explaining the non-linear behavior of AS is discussed. [ABSTRACT FROM AUTHOR]

We have investigated the pulse-width and magnetic-field dependences of current-induced magnetization switching in a (Ga,Mn)As/GaAs/(Ga,Mn)As magnetic tunnel junction. Critical current to induce magnetization switching shows a linear dependence on pulse width from 10 to 1000 μs. The magnetic-field dependence appears to indicate that the observed current-induced magnetization switching proceeds through metastable magnetization structures. [ABSTRACT FROM AUTHOR]

We have investigated the spin tunneling transport in magnetic tunnel junctions (MTJs) with Co40Fe40B20, Co50Fe50, and Co90Fe10 free layers which were deposited on the lower electrode consisting of the same Co40Fe40B20 reference layer/MgO barrier. The tunnel magnetoresistance (TMR) ratio depends critically on the choice of the free layer; the TMR ratios up to 355% were obtained for the MTJs with Co40Fe40B20 free layers and up to 277% with Co50Fe50 free layers, both of which have highly (001)-oriented bcc structures. No high TMR ratio was observed for the MTJs with Co90Fe10 free layer having a polycrystalline fcc structure. [ABSTRACT FROM AUTHOR]

Antiferromagnet (AFM)/ferromagnet (FM) heterostructures with broken inversion symmetry are perceived to open new opportunities for nonvolatile spintronic devices. Previous studies of such systems have demonstrated an emergence of spin-orbit torques (SOTs) in the heterostructures which are strong enough to bring about magnetization reversal. The impact of broken inversion symmetry and spin-orbit coupling also leads to an emergence of the Dzyaloshinskii-Moriya interaction (DMI) which governs the magnetic configuration and magnetization reversal. In this work, we study the SOT-induced effective fields and DMI in a heterostructure with an antiferromagnetic PtMn layer and a ferromagnetic [Co/Ni] multilayer and compare the results with a reference Pt/ [Co/Ni] system. Magnetotransport measurements reveal the same sign and similar magnitude of SOT-induced effective fields for the two systems while current-induced domain wall motion measurements under in-plane fields reveal the opposite sign and smaller magnitude of DMI at the PtMn/ [Co/Ni] interface compared to the Pt/[Co/Ni]. The obtained results offer in-depth information concerning the manifestations of spin-orbit interactions in AFM/FM systems, which is key to understanding of static magnetic configuration and magnetization reversal for their possible applications in antiferromagnetic spintronics. [ABSTRACT FROM AUTHOR]

We have investigated the current-driven magnetization reversal of exchange-biased spin-valve giant magnetoresistive nanopillars with a magnetically pinned ferromagnetic layer. Current-driven magnetization reversal of a ferromagnetic layer with a smaller MV (M: magnetization, V: volume) value is found to take place even when the layer is pinned by the exchange bias induced by an antiferromagnet. The critical current density Jc of the spin-valve nanopillar with a MnIr layer adjacent to the current-driven free layer is of the same order as that of a Co/Cu/Co nanopillar (∼107 A/cm2). [ABSTRACT FROM AUTHOR]

An array of exchange biased spin-valve giant-magnetoresistance nanopillars was fabricated and the current I dependence of the resistance R was investigated using an electrically conducting atomic-force microscope (AFM) probe contact at room temperature. We observed current induced switching in a MnIr/CoFe/Cu/CoFe/NiFe nanopillar using the AFM probe contact. Current-driven switching using nanoprobe contact is a powerful method for developing nonvolatile and rewritable magnetic memory with high density. [ABSTRACT FROM AUTHOR]

(Ga, Mn)As films with high nominal Mn concentration (00.1, which turn to polycrystalline features when x>0.3. X-ray diffraction shows the formation of MnAs together with the growth of (Ga, Mn)As. The lattice constant of the layers suggests that (Ga, Mn)As with high Mn composition as high as 17% can be grown by LT-MBE. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The spin-dependent scattering in ferromagnet/nonmagnet/ferromagnet (Ga,Mn)As/(Al,Ga)As/(Ga,Mn)As trilayer structures was studied. An increase of sheet resistance was observed when the magnetizations of the two ferromagnetic (Ga,Mn)As layers were aligned anti-parallel, which was realized by the different coercivity of the two (Ga,Mn)As layers with different compositions. This is the first demonstration of spin-dependent scattering in magnetic multilayer structures made of semiconductor-materials alone. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The preparation of dilute alloy of GaSb and Mn, (Ga, Mn)Sb, with a few percent of Mn by molecular beam epitaxy and its magnetotransport properties are reported. Magnetotransport measurements show a pronounced anomalous Hall effect and negative magnetoresistance below 50 K. The results suggest that Mn atoms are incorporated in the GaSb host, resulting in the formation of the ferromagnetic semiconductor, (Ga, Mn)Sb. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We investigate the magnetization-reversal mode in CoFeB/MgO magnetic tunnel junctions with perpendicular easy axis from the magnetic-field-angle dependence of coercivity. The reversal in a free layer with diameter of ~20 nm is found to be in a good agreement with coherent reversal mode for a device with a reference layer much larger than the free layer. However, the reversal mode is quite different in a junction in which the two layers are almost the same size. From micro-magnetic simulation, the difference is attributed to the reduction of the magnetic anisotropy in the vicinity of the device edge. [ABSTRACT FROM AUTHOR]

We study current-induced magnetization switching properties of a magnetic tunnel junction with junction diameter of 19 nm and resistance-area product of 6 Ωμm2 in the nanosecond regime with and without in-plane magnetic field. At zero field, for both parallel (P)-to-anti-parallel (AP) and AP-to-P switchings, the probability of switching PSW approaches unity with the increase of pulse voltage duration τP. However, under in-plane magnetic field, PSW for P-to-AP switching starts to saturate at a value lower than unity with increasing τP, while AP-to-P switching remains the same as in the absence of in-plane magnetic field. This in-plane field dependence of PSW can be partially explained by the influence of electric-field modulation of magnetic anisotropy. [ABSTRACT FROM AUTHOR]

Creep motion of magnetic domain wall (DW), thermally activated DW dynamics under subthreshold driving forces, is a paradigm to understand the interaction between driven interfaces and applied external forces. Previous investigation has shown that DW in a metallic system interacts differently with current and magnetic field, manifesting itself as different universality classes for the creep motion. In this article, we first review the experimental determination of the universality classes for current- and field-driven DW creeps in a Ta/CoFeB/MgO wire, and then elucidate the underlying factors governing the obtained results. We show that the nature of torque arising from current in association with DW configuration determines universality class for the current-induced creep in this system. We also discuss the correlation between the field-induced DW creep characteristics and structure observed by a transmission electron microscope. The observed results are expected to provide a deeper understanding for physics of DW motion in various magnetic materials. [ABSTRACT FROM AUTHOR]

We measure ferromagnetic resonance spectra of sputtered Py (20 nm) on (Bi1-xSbx)2Te3 (~50 nm, x = 0-1) grown by molecular beam epitaxy. The linewidths of the spectra for Py on (Bi1-xSbx)2Te3 are much broader than that of Py directly deposited on a flat Si/SiO2 substrate. We find that the broadening results from spin pumping as well as inhomogeneity in Py induced by surface roughness of underneath (Bi1-xSbx)2Te3. [ABSTRACT FROM AUTHOR]

We investigated properties of perpendicular-anisotropy magnetic tunnel junctions (p-MTJs) with [Co/Pt]-multilayer based synthetic ferrimagnetic reference (SyF) layer at elevated annealing temperature Ta from 350°C to 400°C. Shift field HS defined as center field of minor resistance versus magnetic field curve of the MTJs increased with increase of Ta from 350°C to 400°C. The variation of HS is attributed to the variation of saturation magnetic moment in the SyF reference layer. Cross sectional energy dispersive X-ray spectroscopy analysis revealed that Fe element of CoFeB in the reference layer diffuses to Co/Pt multilayers in the SyF reference layer. [ABSTRACT FROM AUTHOR]

We study spin-orbit torque induced magnetization switching in devices consisting of an antiferromagnetic PtMn and ferromagnetic Co/Ni multilayer with sizes ranging from 5 lm to 50 μm. As the size decreases, switching behavior changes from analogue-like to stepwise with several intermediate levels. The number of intermediate levels decreases with the decreasing size and finally evolves into a binary mode below a certain threshold. The results are found to be explained by a unique reversal process of this system, where ferromagnetic domains comprising a number of polycrystalline grains reverse individually and among the domains both out-of-plane and in-plane components of exchange bias vary. [ABSTRACT FROM AUTHOR]

We study the spin-orbit torque induced magnetization switching in W/CoFeB/MgO heterostructures with W deposited under different sputtering conditions. We show that the crystal structure and resistivity of W depend on the employed sputtering conditions. Switching current of nanoscale devices is smaller while effective anisotropy field is larger for the devices with more resistive W channel deposited at lower sputtering power and higher Ar gas pressure. The effective spin Hall angle evaluated from the switching probability varies by a factor of 2-3 depending on the W resistivity controlled by the sputtering conditions. [ABSTRACT FROM AUTHOR]

Reports the quantum Hall effect of electrons in AlGaAs/Ga[sub1-x]In[subx]As/gallium arsenide pseudomorphic strained heterostructures. Effect of strain in the GaInAs layer; Overview of reciprocal magnetic fields corresponding to the maximum of magnetoresistivity; Number of scattering events by cluster-scattering centers in one orbit area.

Provides information on hydrogenated amorphous carbon films prepared at room temperature by low frequency plasma chemical vapor deposition using methane and hydrogen. Measurement of resistivity and breakdown electric field after deposition; Infrared absorption spectrum of the grown film for the carbon-hydrogen stretching mode region; Raman spectroscopy using argon laser excitation.

We report on the temperature dependence of the magnetic anisotropy in Co/Pd/MgO system, in which magnetic moment in Pd is induced by the magnetic proximity effect. We demonstrate that the magnetic anisotropy is modulated by applying an electric field to the Pd surface. At temperatures below 100K, we find the nonlinear electric-field dependence of the anisotropy with the sign reversal. We obtain a huge anisotropy modulation efficiency of ∼1600 fJ/V m at 10K. [ABSTRACT FROM AUTHOR]

We observe magnetic domain structures of MgO/CoFeB with a perpendicular magnetic easy axis under an electric field. The domain structure shows a maze pattern with electric-field dependent isotropic period. The analysis of the period indicates a major role of the electric-field modulation of interfacial magnetic anisotropy for the observation and possible contribution from electric-field modulation of the exchange stiffness constant. [ABSTRACT FROM AUTHOR]

The control of magnetic Skyrmions confined in a nanometer scale disk using electric field pulses is studied by micromagnetic simulation. A stable Skyrmion can be created and annihilated by an electric field pulse depending on the polarity of the electric field. Moreover, the core direction of the Skyrmion can be switched using the same electric field pulses. Such creation and annihilation of Skyrmions, and its core switching do not require any magnetic field and precise control of the pulse length. This unconventional manipulation of magnetic texture using electric field pulses allows a robust way of controlling magnetic Skyrmions in nanodiscs, a path toward building ultralow power memory devices. [ABSTRACT FROM AUTHOR]