Conditions for the growth of smooth La0.7Sr0.3MnO3 thin films by pulsed electron ablation

We report on the optimisation of the growth conditions of manganite La0.7Sr0.3MnO3 (LSMO) thin films prepared by Channel Spark Ablation (CSA). CSA belongs to pulsed electron deposition methods and its energetic and deposition parameters are quite similar to those of pulsed laser deposition. The method has been already proven to provide manganite films with good magnetic properties, but the films were generally relatively rough (a few nm coarseness). Here we show that increasing the oxygen deposition pressure with respect to previously used regimes, reduces the surface roughness down to unit cell size while maintaining a robust magnetism. We analyse in detail the effect of other deposition parameters, like accelerating voltage, discharging energy, and temperature and provide on this basis a set of optimal conditions for the growth of atomically flat films. The thicknesses for which atomically flat surface was achieved is as high as about 10-20 nm, corresponding to films with room temperature magnetism. We believe such magnetic layers represent appealing and suitable electrodes for various spintronic devices.Comment: original paper, thin film optimization, 25 pages, 9 figure

Role of hydration on the functionality of a proteolytic enzyme α-chymotrypsin under crowded environment

Enzymes and other bio-macromolecules are not only sensitive to physical parameters such as pH, temperature and solute composition but also to water activity. A universally instructive way to vary water activity is the addition of osmotically active but otherwise inert solvents which also mimic the condition of an intercellular milieu. In the present contribution, the role of hydration on the functionality of a proteolytic enzyme α-chymotrypsin (CHT) is investigated by modulating the water activity with the addition of polyethylene glycols (PEG with an average molecular weight of 400). The addition of PEG increases the affinity of the enzyme to its substrate, however, followed by a decrease in the turnover number (k_(cat)). Energetic calculations show that entrance path for the substrate is favoured, whereas the exit channel is restricted with increasing concentration of the crowding agent. This decrease is attributed to the thinning of the hydration shell of the enzyme due to the loss of critical water residues from the hydration surface of the enzyme as evidenced from volumetric and compressibility measurements. The overall secondary and tertiary structures of CHT determined from far-UV and near-UV circular dichroism (CD) measurements show no considerable change in the studied osmotic stress range. From kinetic and equilibrium data, we calculate 115 ± 30 numbers of water molecules to be altered during the enzymatic catalysis of CHT. Spectroscopic observation of water relaxation and rotational dynamics of ANS–CHT complex at various concentrations of the osmoting agent also support the dehydration of the hydration layer. Such dehydration/hydration processes during turnover imply a significant contribution of solvation to the energetics of the conformational changes

Microstructure, Morphology, and Ultrafast Dynamics of a Novel Edible Microemulsion

An edible microemulsion (ME) composed of Tween 80/butyl lactate/isopropyl myristate (IPM)/water has been formulated. Pseudoternary phase diagram of the system contains a large single isotropic region. The phase behavior of the system is also studied at low pH (2.6) and in 0.9% NaCl solution. Conductivity, viscosity, ultrasonic velocity, and compressibility studies find consistent results in the structural transition (from water-in-oil (w/o) to bicontinuous, and from bicontinuous to oil-in-water (o/w)) behavior of the ME. Dynamic light scattering studies reveal the size of the MEs. The absorption and steady state emission spectra of 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM) successfully probe the polarity of the ME at its solvation shell and shows the efficacy of hosting model drug molecules. The rotational anisotropy of the dye has been studied to ascertain the geometrical restriction of the probe molecule. Picosecond-resolved fluorescence spectroscopy applies well to study the relaxation dynamics of water in the solvation shell of the MEs. The study finds strong correlation in the relaxation dynamics of water with the structure of host assembly and offers an edible ME system which could act as a potential drug delivery system and nontoxic nanotemplate for other applications

Tunneling current in magnetic-ferroelectric-superconducting heterostructures

We report the tunneling current behavior of magnetic-ferroelectric-superconducting heterostructures for multistates non-volatile random access memory (NVRAM) elements. A heterostructure of La0.67Sr0.33MnO3 (LSMO) (50 nm)/PbZr0.52Ti0.48O3 (PZT) (5 nm)/Bi-Sr-Ca-Cu2-OX (BSCCO) (100 nm)/LaAlO3 (LAO) architecture was fabricated by pulsed laser deposition technique. The tunneling effects were investigated well above and below the superconducting phase transition temperature $(T_{s}\sim92\ \text{K})$ of the BSCCO bottom electrode. A divergent current and conductance paths were observed for polarization up and down direction above the coercive field of the ferroelectric tunnel barrier. This behaviour was significant below Ts where the moderate effect of the external magnetic field was also observed on the tunneling current. The dynamic conductance G(V) data fitted well with Brinkman's model for both polarizations up and polarization down states which suggest the presence of large tunnel electro-resistance