Review of noise sources in magnetic tunnel junction sensors

Invited Oral Presentation: M-13This journal issue contain selected papers from the Asia-Pacific Data Storage Conference 2010Noise problem limits the sensitivity of magnetic tunnel junction (MTJ) sensors for ultra-low magnetic field applications. Noise analysis not only helps in finding ways to eliminate noise disturbances but also essential for understanding the electronic and magnetic properties of MTJs. These approaches provide insight for optimizing the design of MTJ sensors before fabrication. This paper reviews the noise sources in MTJ sensors reported in recent years. Both the origins and mathematical derivations of the noise sources are presented, illustrating how different factors affecting the performance of MTJ sensors. A brief outlook of challenges in the future is also given. © 2011 IEEE.published_or_final_versio

A magnetically shielded instrument for magnetoresistance and noise characterizations of magnetic tunnel junction sensors

A magnetically shielded setup was developed for characterizing magnetoresistance (MR) and noise properties of magnetic tunneling junction (MTJ) sensors. A mu-metal shielding is installed to avoid the interference of external magnetic disturbance. Both MR curves and noise power spectra of MTJ sensors can be obtained for further data analysis. Moreover, a hard-axis magnetic field can be applied to eliminate the hysteresis and the linear field response of MTJ sensors can be measured. The preliminary measurement results on MTJ sensors are presented to illustrate the characterization capabilities of this setup. © 2010 IEEE.published_or_final_versionThe 2010 IEEE International Conference of Electronic Devices and Solid-State Circuits (EDSSC), Hong Kong, 15-17 December 2010. In Proceedings of EDSSC, 2010, p. 1-

Magnetic tunnel junction sensors with conetic alloy

Poster Session - F. Storage Applications and Others: PF-12This journal issue contain selected papers of APDSC'10Al 2O 3 magnetic tunneling junction (MTJ) sensors were fabricated with Conetic alloy Ni 77Fe 14Cu 5Mo 4 deposited as the free layer and pinned layer for its soft magnetic properties. It was observed that the Al 2O 3 MTJ sensors with Conetic exhibited relatively small easy-axis coercivity. Tunneling magnetoresistance (TMR) and noise measurements were carried out to characterize the sensors. TMR of 9.5% and Hooge parameter of 3.825 × 10 -7μm 2 were achieved without any hard-axis field. Hard-axis bias field was applied to eliminate the hysteresis and improve the linear field response of the MTJ sensor. The hysteresis was removed by applying an external magnetic field along the hard axis at 8 Oe and the sensor sensitivity was 0.4 %/Oe within a linear region at room temperature. The relationship between the Hooge parameter and hard-axis field was also investigated and the result demonstrated that the 1/f noise can be suppressed by an optimized hard-axis bias field. This work shows that it is feasible to use Conetic alloy as the soft magnetic layers in MTJ sensors for its small coercivity, and a hard-axis bias field can be used to linearize the sensor response and suppress the 1/f noise. © 2011 IEEE.published_or_final_versionThe Asia-Pacific Data Storage Conference (APDSC'10), Hualien, Taiwan, 27-29 October 2010. In IEEE Transactions on Magnetics, 2011, v. 47 n. 3, p. 714-71

Evolution of superconductivity in K2-xFe4+ySe5: Spectroscopic studies of X-ray absorption and emission.

This study investigates the evolution of superconductivity in K2-xFe4+ySe5 using temperature-dependent X-ray absorption and resonant inelastic X-ray scattering techniques. Magnetization measurements show that polycrystalline superconducting (SC) K1.9Fe4.2Se5 has a critical temperature (T c) of ∼31 K with a varying superconducting volume fraction, which strongly depends on its synthesis temperature. An increase in Fe-structural/vacancy disorder in SC samples with more Fe atoms occupying vacant 4d sites is found to be closely related to the decrease in the spin magnetic moment of Fe. Moreover, the nearest-neighbor Fe-Se bond length in SC samples exceeds that in the non-SC (NS) sample, K2Fe4Se5, which indicates a weaker hybridization between the Fe 3d and Se 4p states in SC samples. These results clearly demonstrate the correlations among the local electronic and atomic structures and the magnetic properties of K2-xFe4+ySe5 superconductors, providing deeper insight into the electron pairing mechanisms of superconductivity

Magnetic tunnel junction magnetic field sensor design tool

A spreadsheet-based magnetic tunnel junction (MTJ) sensor design tool is presented in this paper. The system is developed using Excel and Visual Basic Application. It allows users to optimize the various parameters of the sensor design with the goal of SQUID-like sensitivity. Users can input parameters of the design including magnetic properties, junction areas, and free layers thicknesses. The design tool will then calculate and display automatically various noise sources including Johnson noise, shot noise, 1/f noise, and thermal magnetic noise that must be considered when building MTJ magnetic field sensors. Graphs predicting the sensitivities, operating current and power of the finished sensors are shown and fine tuning of each design parameter is allowed using the scrollbars provided. Using this design tool, effects of changes made to any design parameter can be clearly observed and detailed noise analysis can be studied without manually repeating complex calculations. ©2010 IEEE.published_or_final_versionThe 3rd International Nanoelectronics Conference (INEC 2010), Hong Kong, China, 3-8 January 2010. In Proceedings of the 3rd INEC, 2010, p. 1149-115

Enhancement of sp(3)-bonding in high-bias-voltage grown diamond-like carbon thin films studied by x-ray absorption and photoemission spectroscopy

[[abstract]]X-ray absorption near-edge structure (XANES) and valence-band photoemission spectroscopy (VB-PES) were used to elucidate the electronic and mechanical properties of diamond-like carbon (DLC) thin films deposited by the plasma-enhanced chemical vapour deposition method at various bias voltages (Vb) using a C2H2 vapour precursor in an Ar+ atmosphere. The increase of Vb is found to increase and decrease the contents of sp3- and sp2-bonded carbon atoms, respectively, i.e. the films become more diamond-like. The Young's modulus measurements show increases with the increase of the presence of sp3-bonded carbon atoms in the structure of the DLC films.[[notice]]補正完

Electronic properties of a-CNx thin films: An x-ray-absorption and photoemission spectroscopy study

[[notice]]補正完畢[[booktype]]紙本[[booktype]]電子

Electronic structure and bonding properties of Si-doped hydrogenated amorphous carbon films

[[abstract]]This work investigates the C K-edge x-ray absorption near-edge structure (XANES), valence-band photoelectron spectroscopy (PES), and Fourier transform infrared (FTIR) spectra of Si-doped hydrogenated amorphous carbon films. The C K-edge XANES and valence-band PES spectra indicate that the sp2/sp3 population ratio decreases as the amount of tetramethylsilane vapor precursor increases during deposition, which suggest that Si doping% enhances sp3 and reduces sp2-bonding configurations. FTIR spectra show the formation of a polymeric sp3 C–Hn structure and Si–Hn bonds, which causes the Young’s modulus and hardness of the films to decrease with the increase of the Si content.[[incitationindex]]SCI[[booktype]]紙

Use of haplotypes to identify regions harbouring lethal recessive variants in pigs

Additional file 2: Figure S1. Heatmap of the linkage disequilibrium r 2 values between each of the SNPs located within regions 1.1. and 1.2 on SSC1

Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques

[[abstract]]The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S2− (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S2− species, but significantly increases the concentration of larger S clusters [polysulfides (Sn2−, n > 2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in S-hyperdoped Si samples. Based on the experimental results and the calculations by density functional theory, the chemical state of the S species and the formation of the S-dopant states in the band gap of Si are critical in determining the sub-band gap absorptance of hyperdoped Si samples.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SCI[[ispeerreviewed]]Y[[booktype]]電子版[[countrycodes]]GB