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The current-driven magnetization switching in CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with various free layer materials including synthetic structure was studied in this paper. The MTJ films were deposited on SiO2/Si substrates using RF magnetron sputtering. The tunnel magnetoresistance (TMR) ratios and current-voltage (I-V) characteristics of the the MTJs were measured at room temperature...
In the present work, we show that expansion of the fields in the small parameter 4piomegasigma/c2k2 allows one to tackle the magnon-electron interaction in the system. In particular, it can be applied to the problem of magnons generated by four-magnon scattering after a large angle rotation such is common in modern switching experiments and technological applications such as magnetic recording.
In this study, we investigated that both magnetic switching and tunneling magnetoresistance (TMR) ratio of MTJs with the NiFeSiB free layer. The junctions were fabricated by a photolithographic patterning procedure and ion beam etching. A magnetic field of 100 Oe was applied during deposition to induce the uniaxial magnetic anisotropy in ferromagnetic layer.The NiFeSiB layers were used to substitute...
It has been suggested that magnetization switching dynamics at low energy damping could result in severe write field loss at high data rate for perpendicular recording. To experimentally study the possible dynamic effect and to investigate write field loss at extremely high data rates for today's state-of-the-art perpendicular write heads, recording tests at data rates beyond 2 Gbits/sec-ond are performed...
This article reports the effect of varying the damping in different individual sections of the perpendicular recording head (like the yoke, pole and soft underlayer (SUL) regions) affects the head switching speed. Two head designs were used: the shielded head and monopole head design. The head model used in this paper divided the head into five regions: a) soft underlayer, b) tip, c) confluence, d)...
This paper investigates the switching speed in samples having different surfaces (hereafter quoted as "small" or "large" samples), and compares the temperature dependences thereof. The "large" samples are pseudo-spin valves Co75Fe25 (2.5 nm)/Cu(6 nm)/Co75Fe25(40 nm). The top (thin) layer is patterned into an ellipse of size 150times85 nm, while the bottom layer is unpatterned...
In this research, the angle dependance of Hall voltage and pulse-induced magnetization switching (PIMS) have been studied by electrical transport measurements in the Hall-bar shaped (Ga,Mn)As. Planar Hall data might be governed by a magnetization switching at low field and also the switching could be easily induced by voltage pulses. When the amplitude of the pulse is higher, the switching is more...
Understanding the microscopic mechanisms governing fast magnetic switching processes is of high fundamental interest as well as of vital technological importance. A macrospin picture often fails to adequately describe the situation in extended systems. A detailed study of the magnetization dynamics in complex magnetic materials thus requires a real-space mapping of the magnetization distribution in...
This paper will give a detailed comparison of the Stoner-Wohlfarth type MRAM (SW-MRAM) and the biased zero total anisotropy (ZTA) toggle mode MRAM (T-MRAM) in the aspects of operating fields and their operating field margin ratios.
For toggle MRAM, the free layer is a synthetic antiferromagnet (SAF) that must have specific magnetic properties such as: low magnetostriction, a repeatable saturation field (Hsat) that can be adjusted within a specific range, and a well-defined and reproducible intrinsic anisotropy axis. The results from fully-functional Mb-scale MRAM circuits using CoFeB SAF free layers optimized for toggle switching...
We present a complete study of the influence of thermal activation on the DW mode, the toggle mode, and on the separate first and second pulses of the toggle sequence. To obtain these results, we developed a novel technique that employs a train of three-pulse packets. We found good agreement with a single energy barrier (Eb) thermal activation model for both the DW and toggle modes, indicating excellent...
When injected spin polarized electrons interact with the magnetic moment of a free layer, their angular momentum becomes transferred to the free layer. If sufficient current is applied, the exerted torque switches the free layer either parallel or anti-parallel to the pinned layer depending on the direction of flow of the current. This type of localized current switching is attractive for an MRAM...
In this study we report variable footprint shapes indicating recording pole instability. We extend the spin-stand "footprint" measurements to also evaluate recording pole instability. The observed recording pole instability causes degradation of the system performance and should be avoided. The switching between these states is random and occurs after high frequency head excitation. The...
In this paper we report CIMS in CPP-GMR spin valve elements with longitudinal permanent magnet bias and present sense current density limit without CIMS.
A composite nanowire geometry consisting of soft magnetic (Ni) nanowire lower part and hard magnetic (CoPt) L10 nanowire upper part, has been prepared by electrodeposition into anodized aluminum oxide (AAO) nanopores with ~20-30 nm diameter, ~100 nm tall. The as-deposited nanowires within the AAO pores were then annealed at 700 degree C for 1 hour for conversion to L10 phase. The The microstructure...
The authors measured the remanent magnetization curves for a series of CoPtCr-SiO2 perpendicular media with various thickness at low and high applied field sweep rates. They discussed the "intrinsic" switching field distribution (SFD) caused by the variations in the grain-to-grain switching field. Magnetic analysis revealed the values of the saturation magnetization and the uniaxial magnetic...
In the present study, the switching field distribution (SFD) of the Tb/Pt/Ru/CoPtCr-SiO2 perpendicular media has been studied in relation to the Ar pressure at which the recording layer was deposited. The goal of the present study is to correlate the SFDs of the Tb/Pt/Ru/CoPtCr-SiO2 media with their intergranular exchange coupling and their grain size distribution.
In this study, wrong points of conventional Sharrock's formula are investigated based on the micromagnetic simulation and the method for obtaining correct values for Kb and Hero is discussed.
In this paper we will describe a study of the effects of texture of magnetization reversal and magnetic viscosity in longitudinal thin film media. The issue of magnetic viscosity which leads directly to thermal loss of data is not fully understood in all media systems and the physics of the interrelation remains to be explained.
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