Optimization of the extraordinary magnetoresistance in semiconductor-metal hybrid structures for magnetic-field sensor applications

Semiconductor-metal hybrid structures can exhibit a very large geometrical magnetoresistance effect, the so-called extraordinary magnetoresistance (EMR) effect. In this paper, we analyze this effect by means of a model based on the finite element method and compare our results with experimental data. In particular, we investigate the important effect of the contact resistance $\rho_c$ between the semiconductor and the metal on the EMR effect. Introducing a realistic $\rho_c=3.5\times 10^{-7} \Omega{\rm cm}^2$ in our model we find that at room temperature this reduces the EMR by 30% if compared to an analysis where $\rho_c$ is not considered.Comment: 4 pages; manuscript for MSS11 conference 2003, Nara, Japa

Inhibitors of trypanosoma cruzi Sir2 related protein 1 as potential drugs against Chagas disease.

Chagas disease remains one of the most neglected diseases in the world despite being the most important parasitic disease in Latin America. The characteristic chronic manifestation of chagasic cardiomyopathy is the region's leading cause of heart-related illness, causing significant mortality and morbidity. Due to the limited available therapeutic options, new drugs are urgently needed to control the disease. Sirtuins, also called Silent information regulator 2 (Sir2) proteins have long been suggested as interesting targets to treat different diseases, including parasitic infections. Recent studies on Trypanosoma cruzi sirtuins have hinted at the possibility to exploit these enzymes as a possible drug targets. In the present work, the T. cruzi Sir2 related protein 1 (TcSir2rp1) is genetically validated as a drug target and biochemically characterized for its NAD+-dependent deacetylase activity and its inhibition by the classic sirtuin inhibitor nicotinamide, as well as by bisnaphthalimidopropyl (BNIP) derivatives, a class of parasite sirtuin inhibitors. BNIPs ability to inhibit TcSir2rp1, and anti-parasitic activity against T. cruzi amastigotes in vitro were investigated. The compound BNIP Spermidine (BNIPSpd) (9), was found to be the most potent inhibitor of TcSir2rp1. Moreover, this compound showed altered trypanocidal activity against TcSir2rp1 overexpressing epimastigotes and anti-parasitic activity similar to the reference drug benznidazole against the medically important amastigotes, while having the highest selectivity index amongst the compounds tested. Unfortunately, BNIPSpd failed to treat a mouse model of Chagas disease, possibly due to its pharmacokinetic profile. Medicinal chemistry modifications of the compound, as well as alternative formulations may improve activity and pharmacokinetics in the future. Additionally, an initial TcSIR2rp1 model in complex with p53 peptide substrate was obtained from low resolution X-ray data (3.5 Å) to gain insight into the potential specificity of the interaction with the BNIP compounds. In conclusion, the search for TcSir2rp1 specific inhibitors may represent a valuable strategy for drug discovery against T. cruzi

Low-noise magnetic-flux sensors based on the extraordinary magnetoresistance effect

We report noise measurements on Au–InAs hybrid structures involving a high-mobility two-dimensional electron system. Such structures show the extraordinary magnetoresistance (EMR) effect. We find excellent noise performance at room temperature close to the Johnson noise, which is in particular important for a technical application. At 4.2 K and in a magnetic field of about 1 T the nonoptimized EMR device is found to exhibit a low magnetic fluxnoise, offering the perspective of sensor applications also in a high magnetic field and at cryogenic temperature

Effect of the Interface Resistance on the Extraordinary Magnetoresistance of Semiconductor/Metal Hybrid Structures

We report on magnetotransport experiments performed at 4.2 K on hybrid structures consisting of a metal and a mesoscopic two-dimensional electron system in an InAs/InGaAs heterostructure. The devices were fabricated using cleaved-edge overgrowth. We find that they exhibit an extraordinary magnetoresistance effect (EMR) which is most pronounced in the case of the lowest specific contact resistance ρ i of ≈10−8 Ω cm2 achieved in this work. The largest relative resistance change Δ R/R is 115,000% at a magnetic field B = 1 T. A systematic study of the performance of the EMR devices with down to sub-μm lateral dimension and with different ρ i is reported

Extraordinary magnetoresistance effect in a microstructured metal–semiconductor hybrid structure

We have fabricated hybrid structures consisting of a metallic thin film and of a microstructured two-dimensional electron system in an InAsheterostructure. The devices are found to exhibit a huge magnetoresistance(MR)effect in magnetic fields ⩽1 T . At low temperature, a value of ΔR/R=[R(B=1 T )−R(B=0)]/R(B=0) as high as 115 000% is measured. The value of ΔR/R has been studied as a function of the electron mobility, the electron density and the lateral width of the semiconductor. We find that the MReffect can be tailored by these different parameters and technological relevant devices can be realized