Two-phase structure of ultra-thin La-Sr-MnO films

The structural, electrical and magnetic properties of ultra-thin La_0.83Sr_0.17MnO₃ (LSMO) films, deposited on NdGaO₃ substrate by using the MOCVD technique, were studied. The film thickness d varied in the range from 4 to 140 nm. X-ray and RHEED measurements demonstrated that the films had a two-phase structure. One phase had an orthorhombic face centred structure (a = 0.406 nm and c = 0.46 nm), while the other one had a cubic perovskite-like structure with a = 0.388 nm. Low field dc resistance and magnetization vs. temperature dependences were investigated in the temperature range from 5 to 300 K using a conventional four-probe method and a SQUID magnetometer. It was found that the temperature of the resistivity maximum, T_m, increases with increasing film thickness and that the value of the Curie temperature T_C estimated from the temperature dependence of magnetization is very close to T_m. Modelling of the remanent magnetization vs. temperature dependence based on a two-phase model was in agreement with experimental results. This model also explains the T_m shift to lower temperatures with decreasing film thickness.     

Colossal Magnetoresistance Properties of La0.83Sr0.17MnO3 Thin Films Grown by MOCVD on Lucalox Substrate

The magnetoresistance (MR) of polycrystalline La_0.83Sr_0.17MnO₃ thin films have been studied in high pulsed magnetic fields up to 38 T in the temperature range 100–300 K. The lucalox substrates were used to obtain polycrystalline structures with naturally formed grain boundaries (GBs) and crystallites whose dimensions were determined by film deposition temperature. It was found that the MR value is highest in the films having smallest crystallites. The main behaviour of high-field MR was analysed using modified Mott’s hopping model assuming that the GBs might be ferromagnetic with a Curie temperature T _C being reduced in comparison with that of the crystallites interior.     

Measurement of Nanomolar Dissociation Constants by Titration Calorimetry and Thermal Shift Assay �C Radicicol Binding to Hsp90 and Ethoxzolamide Binding to CAII

The analysis of tight protein-ligand binding reactions by isothermal titration calorimetry (ITC) and thermal shift assay (TSA) is presented. The binding of radicicol to the N-terminal domain of human heat shock protein 90 (Hsp90αN) and the binding of ethoxzolamide to human carbonic anhydrase (hCAII) were too strong to be measured accurately by direct ITC titration and therefore were measured by displacement ITC and by observing the temperature-denaturation transitions of ligand-free and ligand-bound protein. Stabilization of both proteins by their ligands was profound, increasing the melting temperature by more than 10 ºC, depending on ligand concentration. Analysis of the melting temperature dependence on the protein and ligand concentrations yielded dissociation constants equal to 1 nM and 2 nM for Hsp90αN-radicicol and hCAII-ethoxzolamide, respectively. The ligand-free and ligand-bound protein fractions melt separately, and two melting transitions are observed. This phenomenon is especially pronounced when the ligand concentration is equal to about half the protein concentration. The analysis compares ITC and TSA data, accounts for two transitions and yields the ligand binding constant and the parameters of protein stability, including the Gibbs free energy and the enthalpy of unfolding.