10 research outputs found
Diffusion based degradation mechanisms in giant magnetoresistive spin valves
Spin valve systems based on the giant magnetoresistive (GMR) effect as used
for example in hard disks and automotive applications consist of several
functional metallic thin film layers. We have identified by secondary ion mass
spectrometry (SIMS) two main degradation mechanisms: One is related to oxygen
diffusion through a protective cap layer, and the other one is interdiffusion
directly at the functional layers of the GMR stack. By choosing a suitable
material as cap layer (TaN), the oxidation effect can be suppressed.Comment: 3 pages, 3 figures. to be published in Appl. Phys. Let
Controlled data storage for non-volatile memory cells embedded in nano magnetic logic
Among the beyond-CMOS technologies, perpendicular Nano Magnetic Logic (pNML) is a promising candidate due to its low power consumption, its non-volatility and its monolithic 3D integrability, which makes it possible to integrate memory and logic into the same device by exploiting the interaction of bi-stable nanomagnets with perpendicular magnetic anisotropy. Logic computation and signal synchronization are achieved by focus ion beam irradiation and by pinning domain walls in magnetic notches. However, in realistic circuits, the information storage and their read-out are crucial issues, often ignored in the exploration of beyond-CMOS devices. In this paper we address these issues by experimentally demonstrating a pNML memory element, whose read and write operations can be controlled by two independent pulsed currents. Our results prove the correct behavior of the proposed structure that enables high density memory embedded in the logic plane of 3D-integrated pNML circuits
Spin-canting effects in GMR sensors with wide dynamic field range
Magnetoresistive (xMR) sensors find extensive application in science and
industry, replacing Hall sensors in various low field environments. While there
have been some efforts in increasing the dynamic field range of xMR sensors,
Hall sensors remain to dominate high field applications due to their wide
linear range. Using a perpendicular magnetized reference system and an in-plane
free layer allows us to overcome this disadvantage of xMR sensors, and,
furthermore, investigate spin-canting effects in interlayer exchange coupled
perpendicular synthetic antiferromagnets (p-SAF). We created p-SAFs with
exchange coupling fields of up to 10 kOe, based on magnetic Co/Pt multilayer
systems. The p-SAFs are either designed as "single" p-SAFs, where two Co/Pt
multilayers are interlayer exchange coupled via a 4 {\AA} thick Ru spacer, or
as "double" p-SAFs, where an additional Co layer is interlayer exchange coupled
to the top multilayer. These p-SAFs are used for giant magnetoresistance (GMR)
sensors with wide dynamic field range. By using a p-SAF as the reference system
and employing an in-plane magnetic layer as the GMR's free layer, the linear
range can be effectively increased limited only by the p-SAF's switching
fields. Additionally, the magnetic anisotropy of the in-plane free layer is
fully controlled, which allows saturation fields by design. Different
configurations were investigated, ranging from free layer magnetic saturation
at lower to far higher fields than the p-SAF's switching fields. We can show
through micromagnetic simulations that certain GMR transfer curves are
dominated by spin-canting effects in the interlayer exchange coupled reference
system. Finally, our simulation results lay out the correlation of the p-SAF's
design parameters and its magnetization reversal behavior.Comment: 9 pages, 10 figures, 1 tabl
Impact of blocking temperature distribution on the thermal behavior of MnIr and MnPt magnetoresistive stacks
Controlled data storage for non-volatile memory cells embedded in nano magnetic logic
Among the beyond-CMOS technologies, perpendicular Nano Magnetic Logic (pNML) is a promising candidate due to its low power consumption, its non-volatility and its monolithic 3D integrability, which makes it possible to integrate memory and logic into the same device by exploiting the interaction of bi-stable nanomagnets with perpendicular magnetic anisotropy. Logic computation and signal synchronization are achieved by focus ion beam irradiation and by pinning domain walls in magnetic notches. However, in realistic circuits, the information storage and their read-out are crucial issues, often ignored in the exploration of beyond-CMOS devices. In this paper we address these issues by experimentally demonstrating a pNML memory element, whose read and write operations can be controlled by two independent pulsed currents. Our results prove the correct behavior of the proposed structure that enables high density memory embedded in the logic plane of 3D-integrated pNML circuits
Comparison of Sensitivity and Low-Frequency Noise Contributions in Giant-Magnetoresistive and Tunneling-Magnetoresistive Spin-Valve Sensors with a Vortex-State Free Layer
Magnetoresistive spin valve sensors based on the giant- (GMR) and tunnelling-
(TMR) magnetoresisitve effect with a flux-closed vortex state free layer design
are compared by means of sensitivity and low frequency noise. The vortex state
free layer enables high saturation fields with negligible hysteresis, making it
attractive for applications with a high dynamic range. The measured GMR devices
comprise lower pink noise and better linearity in resistance but are less
sensitive to external magnetic fields than TMR sensors. The results show a
comparable detectivity at low frequencies and a better performance of the TMR
minimum detectable field at frequencies in the white noise limit.Comment: 6 pages, 6 figure
Ralstonia eutropha H16 Flagellation Changes According to Nutrient Supply and State of Poly(3-Hydroxybutyrate) Accumulationâ–ż
Two-dimensional polyacrylamide gel electrophoresis (2D PAGE), in combination with matrix-assisted laser desorption ionization-time of flight analysis, and the recently revealed genome sequence of Ralstonia eutropha H16 were employed to detect and identify proteins that are differentially expressed during different phases of poly(3-hydroxybutyric acid) (PHB) metabolism. For this, a modified protein extraction protocol applicable to PHB-harboring cells was developed to enable 2D PAGE-based proteome analysis of such cells. Subsequently, samples from (i) the exponential growth phase, (ii) the stationary growth phase permissive for PHB biosynthesis, and (iii) a phase permissive for PHB mobilization were analyzed. Among several proteins exhibiting quantitative changes during the time course of a cultivation experiment, flagellin, which is the main protein of bacterial flagella, was identified. Initial investigations that report on changes of flagellation for R. eutropha were done, but 2D PAGE and electron microscopic examinations of cells revealed clear evidence that R. eutropha exhibited further significant changes in flagellation depending on the life cycle, nutritional supply, and, in particular, PHB metabolism. The results of our study suggest that R. eutropha is strongly flagellated in the exponential growth phase and loses a certain number of flagella in transition to the stationary phase. In the stationary phase under conditions permissive for PHB biosynthesis, flagellation of cells admittedly stagnated. However, under conditions permissive for intracellular PHB mobilization after a nitrogen source was added to cells that are carbon deprived but with full PHB accumulation, flagella are lost. This might be due to a degradation of flagella; at least, the cells stopped flagellin synthesis while normal degradation continued. In contrast, under nutrient limitation or the loss of phasins, cells retained their flagella