La 0.5 Sr 0.5 MnO 3 thin films were deposited onto sapphire substrates by means of the pulsed-laser deposition technique. These films were characterized by several techniques including x-ray diffraction, Rutherford backscattering spectrometry, energy-dispersive x-ray, atomic-force microscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy (XPS). The cation ratios are the same in the deposited films as in the target. However, strontium segregation occurs at the film surface with an enrichment in this element compared to Mn and La, as shown by XPS. In addition, a clear correlation between the three different contributions which compose the O(1s) XPS signal and the Sr, La, and Mn surface concentrations has been established. Annealing the films at a sufficiently high-temperature produces the same crystal structure as in the target.

Ion transport in crystalline solids is an essential process for many electrochemical energy converters such as solid‐state batteries and fuel cells. Empirical data have shown that ion transport in crystal lattices obeys the Meyer‐Neldel Rule (MNR). For similar, closely related materials, when the material properties are changed by doping or by strain, the measured ionic conductivities showing different activation energies intersect on the Arrhenius plot, at an isokinetic temperature. Therefore, the isokinetic temperature is a critical parameter for improving the ionic conductivity. However, a comprehensive understanding of the fundamental mechanism of MNR in ion transport is lacking. Here the physical significance and applicability of MNR is discussed, that is, of activation entropy‐enthalpy compensation, in crystalline fast ionic conductors, and the methods for determining the isokinetic temperature. Lattice vibrations provide the excitation energy for the ions to overcome the activation barrier. The multi‐excitation entropy model suggests that isokinetic temperature can be tuned by modulating the excitation phonon frequency. The relationship between isokinetic temperature and isokinetic prefactor can provide information concerning conductivity mechanisms. The need to effectively determine the isokinetic temperature for accelerating the design of new fast ionic conductors with high conductivity is highlighted.

The performance of giant magneto-impedance (GMI)-based magnetometers is currently limited by the noise due to the electronic conditioning circuitry. We propose a simple model of this noise for a GMI sensor using a synchronous detection scheme. The GMI sensing element consists of a thin pick-up coil wound around a Co-rich amorphous micro-wire. It is fully described by a two port network model and associated impedance matrix. Noise and sensitivity behavior are studied for the four measuring configurations, corresponding to four terms of the impedance matrix. The model yields a good description of experimental data from noise measurements. The magnetic noise spectral density is dominated either by the excitation or detection stages, depending upon whether the excitation currents are high or low. The nontrivial noise behavior exhibited by each configuration leads to better understanding of the noise limitations of GMI magnetometers. The configuration in which the signal at the coil terminals is measured (often called offdiagonal) is the most efficient in decreasing the equivalent output magnetic noise spectral density.

Giant magnetoimpedance (GMI) at 10 MHz and longitudinal magnetization curves are used to investigate the anisotropy of ${\mathrm{Co}}_{\mathrm{68.15}}{\mathrm{Fe}}_{\mathrm{4.35}}{\mathrm{Si}}_{\mathrm{12.5}}{\mathrm{B}}_{\mathrm{15}}$ wires, glass-covered and after glass removal. The high resolution GMI response to the field shows hysteresis and large Barkhausen jumps, in good agreement with those observed in the magnetization curves. These are modeled through superposition of the response of the inner core and outer shell of the wires. The GMI response is calculated using the differential susceptibility deduced from the model, thus relating the domain structure to the observed magnetoimpedance.

The effect of magnetocrystalline anisotropy and dipolar interactions in Co nanowire arrays is studied by ferromagnetic resonance (FMR). Microwave measurements performed by the microstripline method are reported for two series of crystalline hcp Co (with the $c$ axis nominally perpendicular $\left[\text{Co}\left(c\perp \right)\right]$ and parallel to the wires $\left[\text{Co}\left(c\parallel \right)\right]$ ) and an amorphous alloy with Co as the main component—${\text{Co}}_{94}{\text{Fe}}_5{\text{B}}_1$ . Extrapolation of the high field linear part of the resonance curve (frequency versus dc field) permitted an evaluation of the effective anisotropy fields for saturated samples, as well as of the intrinsic fields $H_K$ , showing that the great differences between the three series are due to the magnetocrystalline anisotropy. The $H_K$ values for the two series of Co are discussed in terms of a model which accounts for the effect of the distributions of the $c$ axis orientation in systems of uniaxial ferromagnets. The observed dependence of the effective anisotropy fields on the array geometry (wire length and diameter) is interpreted in terms of the interwire dipolar interactions and found to be in agreement with theoretical predictions based on a micromagnetic model. The fact that the resonance frequencies at $H_{\text{dc}}=0$ are geometry dependent shows that magnetostatic interactions are still significant at remanence. A second series of FMR experiments was performed at constant frequency (38 GHz), with the purpose of obtaining the angle dependence of the resonance field. These experiments provided an alternative method for the evaluation of the effective anisotropy field. The angle dependence of the resonance field for $\text{Co}\left(c\perp \right)$ fitted the simplest equation for magnets with uniaxial anisotropy, obtained considering only the first order term in the expression of the magnetocrystalline energy as a function of the magnetization orientation. The same is not true for $\text{Co}\left(c\parallel \right)$ , which required inclusion of a second order term.