We report electrical manipulation of magnetization processes in a ferromagnetic semiconductor, which low-density carriers are responsible for the interaction. The coercive force H C at reversal occurs can be manipulated by modifying carrier density through application electric fields gated structure. Electrically assisted reversal, as well demagnetization, has been demonstrated effect. This offers functionality not previously accessible magnetic materials and may become useful reversing...

Solid understanding of current induced torques is key to the development and voltage controlled magnetization dynamics in ultrathin magnetic heterostructures. To evaluate size direction such torques, or effective fields, a number methods have been employed. Here we examine adiabatic (low frequency) harmonic Hall measurement that has used study field. We derive an analytical formula for voltages field both out plane in-plane magnetized systems. The agrees with numerical calculations based on...

The electric field-induced ∼180° magnetization reversal is realized for a sputtered CoFeB/MgO-based magnetic tunnel junction with perpendicular easy axis in static external field. Application of bias voltage nanoseconds duration results temporal change the free layer CoFeB to in-plane, which induces precessional motion layer. takes place when pulse adjusted half period precession. We show that back and forth can be observed by using successive application half-period pulses.

We investigated perpendicular CoFeB-MgO magnetic tunnel junctions (MTJs) with a recording structure consisting of two interfaces, MgO/CoFeB (1.6 nm)/Ta (0.4 nm)/CoFeB (1.0 nm)/MgO. Thermal stability factor MTJ the having junction size 70 nmφ was increased by 1.9 from highest value MTJs single interface same device structure. On other hand, intrinsic critical current for spin transfer torque switching double- and single-interface comparable.

We investigate properties of perpendicular anisotropy magnetic tunnel junctions (MTJs) with a recording structure MgO/CoFeB/Ta/CoFeB/MgO down to junction diameter (D) 11 nm from 56 nm. Thermal stability factor (Δ) MTJ the starts decrease at D = 30 dependence Δ agrees well that expected blanket film taking into account change in demagnetizing factors MTJs. Intrinsic critical current (IC0) reduces entire investigated range. A ratio IC0 shows continuous increase

Current-induced domain-wall motion with velocity spanning over five orders of magnitude up to 22 m/s has been observed by magneto-optical Kerr effect in (Ga,Mn)As perpendicular magnetic anisotropy. The data are employed verify theories spin-transfer the Slonczewski-like mechanism as well torque resulting from spin-flip transitions region. Evidence for creep at low currents is found.

Junction size dependence of critical current (IC0) for spin transfer torque switching and thermal stability factor (E/kBT) was examined in CoFeB/MgO perpendicular magnetic tunnel junctions (p-MTJs). The IC0 increased with increasing recording layer area (Srec). On the other hand, E/kBT showed almost constant values even though Srec from ∼1500 nm2 (44 nmφ) to ∼5000 (76 nmφ). Both behavior can be explained assuming that nucleation type magnetization reversal takes place p-MTJs.

Current-induced domain wall motion in perpendicularly magnetized CoFeB nanowires with a stack structure of Ta(1.0 nm)/CoFeB(1.2 nm)/MgO(2.0 nm)/Ta(1.0 nm) was investigated. Domain driven by adiabatic spin-transfer torque observed at current about 74 μA, corresponding to density 6.2×107 A/cm2. The obtained results were compared those micromagnetic simulation and the spin polarization estimated be 0.72.

The current-induced effective field in perpendicularly magnetized Ta/CoFeB/MgO wire was investigated. A threshold decrease of 6.4 kOe/mA observed by measuring the Hall resistance versus magnetic curve with various bias currents. probably caused in-plane field, mainly due to Rashba effect. smaller and opposite direction compared that Pt/Co/AlOx previously reported.

Domain structures in CoFeB-MgO thin films with a perpendicular easy magnetization axis were observed by magneto-optic Kerr-effect microscopy at various temperatures. The domain wall surface energy was obtained analyzing the spatial period of stripe domains and fitting established models to period. In combination SQUID measurements anisotropy energy, this leads an estimate exchange stiffness width these films. These parameters are essential for determining whether walls will form patterned...

Junction size (D) dependence of thermal stability (Δ) factor and intrinsic critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C0</sub> ) were investigated for MgO/CoFeB/Ta/CoFeB/MgO recording structure in magnetic tunnel junctions (MTJs) having a CoFeB reference layer synthetic ferrimagnetic (SyF) layer. Δ the shows almost constant value down to 40 nm, whereas I linear on area, as similarly observed with single-interface....

We show that the magnetic characteristics of Ta|CoFeB|MgO heterostructures are strongly influenced by doping Ta underlayer with nitrogen. In particular, saturation magnetization drops upon underlayer, suggesting doped acts as a boron diffusion barrier. addition, thickness dead layer decreases increasing nitrogen doping. Surprisingly, interface anisotropy increases to ∼1.8 erg/cm2 when an optimum amount is introduced into underlayer. These results serves good for spintronic applications...

A 32-Mb SPin-transfer torque RAM (SPRAM) chip was demonstrated with an access time of 32 ns and a cell write-time 40 at supply voltage 1.8 V. The fabricated 150-nm CMOS 100 × 200-nm tunnel magneto-resistive (TMR) device element. required thermal stability 67 the TMR estimated by taking into account disturbances during read operations data retention periods 10 years for nonvolatile operation. SPRAM features three circuit technologies suitable large-scale array: 1) two-transistor, one-resistor...

We investigated the dependence of perpendicular magnetic anisotropy in CoFeB-MgO on MgO layer thickness. Magnetization curves show that a clear easy axis is obtainable 1.5-nm thick CoFeB by depositing more than three monolayers. deposited four different buffer layers. Results counter interface CoFeB-nonmagnetic metal affects CoFeB/MgO.

We investigate electric-field effects on the effective magnetic anisotropy energy density Keff and Gilbert damping constant α in Ta/CoFeB/MgO structures with CoFeB thickness t ranging from 1.4 to 1.8 nm by ferromagnetic resonance. The electric field-induced modulation ratio of areal Kefft does not depend thickness, indicating that effect originates CoFeB/MgO-interfacial anisotropy. A clear is observed for structure = nm, almost no ≥ 1.5 nm.

We show a three terminal magnetic tunnel junction (MTJ) with 10-nm thick channel based on an interconnection material Cu 10% Ir doping. By applying current density of less than 1012 A m−2 to the channel, depending direction, switching MTJ defined takes place. that spin transfer torque (STT) plays critical role in determining threshold current. assuming Hall effect being source STT, lower bound magnitude angle is evaluated be 0.03.

We have studied the underlayer thickness and temperature dependences of current induced effective field in CoFeB|MgO heterostructures with Ta based underlayers. The at which saturates is found to be different between two orthogonal components field, i.e. damping-like term tends saturate smaller than field-like term. For large films saturates, we find that significantly influences size field. A striking difference dependence components: decreases whereas increases increasing temperature....

We propose and demonstrate a scheme for magnetization switching in magnetic tunnel junctions, which two successive voltage pulses are applied to utilize both spin-transfer torque electric field effect. Under this scheme, CoFeB/MgO junction with perpendicular easy axis is shown switch faster than by alone more reliably that fields alone.

Magnetic domain wall motion induced by magnetic fields and spin-polarized electrical currents is experimentally well established. A full understanding of the underlying mechanisms, however, remains elusive. For ferromagnetic semiconductor (Ga,Mn)As, we have measured compared such motions in thermally activated subthreshold, or "creep," regime, where velocity obeys an Arrhenius scaling law. Within this law, clearly different exponents current field reflect universality classes, showing that...

Thermal stability factor Δ of the recording layer was studied in perpendicular anisotropy CoFeB/MgO magnetic tunnel junctions (p-MTJs) with various CoFeB thicknesses and junction sizes. In all series p-MTJs different thicknesses, is virtually independent sizes 48-81 nm diameter. The values increase linearly as thickness increases. slope linear fit explained well by a model based on nucleation-type magnetization reversal.

We investigated the effect of using a synthetic ferrimagnetic (SyF) free layer in MgO-based magnetic tunnel junctions (MTJs) on current-induced magnetization switching (CIMS), particularly for application to spin-transfer torque random access memory (SPRAM). The employed SyF had Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">40</sub> Fe B xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> /Ru/Co and...

We review recent developments in magnetic tunnel junctions with perpendicular easy axis (p-MTJs) for nonvolatile very large scale integrated circuits (VLSIs). So far, a number of material systems such as rare-earth/transition metal alloys, L1 0 -ordered ( Co, Fe )– Pt Co /( Pd, ) multilayers, and ferromagnetic-alloy/oxide stacks have been proposed electrodes p-MTJs. Among them, p-MTJs single or double stacks, particularly CoFeB–MgO , were shown to high potential satisfy major requirements...