Influence of Prototropic Reactions on the Absorption and Fluorescence Spectra of Methyl p-dimethylaminobenzoate and Its Two Ortho Derivatives

The influence of prototropic reactions on the spectral characteristics of methyl p-dimethylaminobenzoate (I) and its o-methoxy (II) and o-hydroxy (III) derivatives has been studied using steady-state spectroscopic technique and quantum-chemical calculations. This study concerns the solvent-induced shift of the absorption, locally excited (LE) and intramolecular charge transfer (ICT) fluorescence bands in the neat tetrahydrofuran (THF) and its hydrochloric acid solutions at different HCl concentrations. On the basis of the experimental results and quantum-chemical calculations, it was shown that in a hydrochloric acid solution the studied molecules exist as a mixture of neutral, mono-, and dicationic forms. Additionally, the results of spectroscopic measurements were used to calculate, according to the Benesi-Hildebrand method, the equilibrium constants of protopropic reactions in the ground, S0, and excited, S1, states. Our findings predestine molecules I and II to be used as acid fluorescence probes in a region of 0–2.5 M of [H+] concentrations

Influence of Temperature and Annealing on GMR in Sputtered Permalloy/Cu Multilayers

The influence of temperature and annealing on giant magnetoresistance of Si(100)/Cu(20 nm)/Py(2 nm)/(Cu(2 nm)/Py(2 nm))$\text{}_{100}$ multilayer (Py = Ni$\text{}_{83}$Fe$\text{}_{17}$) sputtered at room temperature in double face-to-face configuration is reported. It was found that giant magnetoresistance value, ΔR$\text{}_{GMR}$/R$\text{}_{sat}$ (where R$\text{}_{sat}$ is the resistance in saturation), monotonically decreases with increasing temperature (4.5% at 173 K to about 1% at 373 K). This results from the decrease in magnetic change of resistance, ΔR$\text{}_{GMR}$, and to the lesser extent from an increase in R$\text{}_{sat}$, though both of them are caused by the shortening of electrons mean free path. The observed almost linear decrease in giant magnetoresistance saturation field with increasing temperature is explained by temperature changes of magnetization profile. Vibrating sample magnetometer measurements revealed that the increase in temperature results in pronounced decrease in remnant to saturation magnetization ratio (M$\text{}_{r}$/M$\text{}_{s}$) suggesting that at low temperatures magnetic bridges between Py layers play an important role in magnetization process. It is shown that proper annealing, by an annihilation of bridges and/or lateral decoupling, leads to an increase in giant magnetoresistance ratio from 3.4% in as deposited state to 4.7%

Co/Au multilayers with graded magnetic anisotropy for magnetic field sensing

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich. - This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively

Domains Stimulated Magnetostatic Coupling in NiFe/Au/Co/Au Multilayers Investigated by Complementary Methods

The magnetic structure of $Ni_{80}Fe_{20}$/Au/Co/Au multilayers characterized by easy-plane and easy-axis perpendicular to the sample plane anisotropies for NiFe and Co, respectively, is strongly modified by magnetostatic coupling resulting from stray fields of stripe domains in the Co layers. Using complementary methods it will be shown that the magnetostatic coupling increases with decreasing Au spacer thickness, with the weakening of the easy plane anisotropy of the NiFe layers and with increasing thickness of the Co layers